Adding and subtracting fractions with the same denominator
By the end of this chapter you will be able to
- Compare and order fractions with the same denominator
- Write equivalent fractions with a small denominator
- Add two fractions with the same denominator, simplifying when needed
- Subtract fractions with the same denominator
- Write a total greater than one as a mixed number, and solve fraction problems with lengths and amounts
You should already know
- Fractions of wholes and amounts (Level 4, chapter 7)
- Halves and quarters of amounts (Level 4, chapter 7)
Where this leads
- Fractions with different denominators (a later level)
- Decimals to tenths and hundredths (chapter 7)
Step-by-step practice: maths (Level 5). Small steps, repeated until fluent. Content: Add and subtract fractions with the same denominator (Y5 paraphrase), Recognise and show, using diagrams, equivalent fractions with a small denominator (Y4 paraphrase), Compare and order fractions with the same denominator (Y5 paraphrase), Solve problems involving fractions of a length or an amount (Y5 paraphrase).
Exercise P Do you remember?
Non-calculatorMethod. Share 14 into 2 equal parts, then take one part.
- Share 14 into 2 equal parts. The bottom number tells us how many parts.14 ÷ 2 = 7
- Take 1 of the parts. The top number is 1.1 × 7 = 7
- Write the answer. This is one half of 14.7
Check. Check: 7 + 7 = 14.
Watch out. Divide by the bottom number first.
Method. Write the whole number, then the tenths after the point.
- Write the whole number. This is the part before the decimal point.2
- Write the tenths. 3/10 is 3 tenths, so the 3 goes after the point.2.3
- Write the answer. A decimal point separates the whole from the tenths.2.3
Check. Check: 3/10 is 0.3, so 2 + 0.3 = 2.3.
Watch out. The first digit after the point is tenths.
Method. Work out the multiplication first.
- Work out 6 × 7. Multiply before you add.6 × 7 = 42
- Add 3. Add the last number.42 + 3 = 45
- Write the answer. This is the total.45
Check. Check: 45 - 3 = 42, and 42 ÷ 6 = 7.
Watch out. Multiply first, then add.
Method. Take away the thousands, then the rest.
- Take away 1,000. Start with the thousands.5,000 - 1,000 = 4,000
- Take away 250. Take away the rest.4,000 - 250 = 3,750
- Write the answer. This is what is left.3,750
Check. Check: 3,750 + 1,250 = 5,000.
Watch out. Check the subtraction by adding back.
Method. Compare the tenths.
- Compare the whole numbers. Both are 0 whole.0 and 0
- Compare the tenths. The bigger tenths digit is the greater decimal.6 tenths and 5 tenths
- Choose the greater decimal. 6 tenths is more than 5 tenths.0.6
Check. Check: 0.6 is 6 tenths; 0.5 is 5 tenths.
Watch out. Compare the tenths digits.
Comparing and ordering fractions, and equal fractions
When fractions have the same bottom number, the parts are the same size. Compare the top numbers: 6/8 is more than 3/8.
Equal fractions have the same value but different names. Half of a bar is the same as 2 parts of 4: 1/2 = 2/4.
Key ideas
- Same bottom number: compare the top numbers.
- Multiply the top and bottom by the same number to find an equal fraction.
- A fraction with the top and bottom equal is one whole.
Method. With the same denominator, compare the numerators.
- Look at the bottom numbers. Both fractions have the same bottom number, so the parts are the same size.Both are 8ths
- Compare the top numbers. With the same size of part, the bigger top number is the bigger fraction.3 and 6
- Choose the greater fraction. The fraction with more parts is greater.6/8
Check. Check: 6 parts is more than 3 parts of the same size.
Watch out. Do not compare the bottom numbers. The bigger the bottom number, the smaller each part.
Method. With the same denominator, the order is the order of the numerators.
- Look at the bottom numbers. They are all the same, so compare the top numbers only.All are 6ths
- Order the top numbers. Smallest top number first.1, 2, 4, 5
- Write the fractions in order. Put the fractions back in the same order.1/6, 2/6, 4/6, 5/6
Check. Check: the first fraction has the fewest parts, and the last has the most.
Watch out. The fractions are the same size if the top numbers are equal. Use the top numbers to order them.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 8. The denominator is multiplied by this number.2 × 4 = 8
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.1 × 4 = 4
- Write the equal fraction. The new fraction has the same value.4/8
Check. Check: 4/8 simplifies to 1/2.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Watch out
Watch out. 3/8 is not greater than 3/4. The bigger bottom number means smaller parts.
Exam tip
Grown-up tip. Fold a strip of paper into 8 and shade 3 parts, then shade 6 parts on another strip. Compare them.
Exercise 6A Practice: comparing, ordering and equal fractions
Non-calculatorMethod. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 4. The denominator is multiplied by this number.2 × 2 = 4
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.1 × 2 = 2
- Write the equal fraction. The new fraction has the same value.2/4
Check. Check: 2/4 simplifies to 1/2.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 6. The denominator is multiplied by this number.2 × 3 = 6
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.1 × 3 = 3
- Write the equal fraction. The new fraction has the same value.3/6
Check. Check: 3/6 simplifies to 1/2.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 12. The denominator is multiplied by this number.4 × 3 = 12
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.3 × 3 = 9
- Write the equal fraction. The new fraction has the same value.9/12
Check. Check: 9/12 simplifies to 3/4.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 6. The denominator is multiplied by this number.3 × 2 = 6
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.1 × 2 = 2
- Write the equal fraction. The new fraction has the same value.2/6
Check. Check: 2/6 simplifies to 1/3.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. With the same denominator, the order is the order of the numerators.
- Look at the bottom numbers. They are all the same, so compare the top numbers only.All are 8ths
- Order the top numbers. Smallest top number first.1, 3, 6, 8
- Write the fractions in order. Put the fractions back in the same order.1/8, 3/8, 6/8, 8/8
Check. Check: the first fraction has the fewest parts, and the last has the most.
Watch out. The fractions are the same size if the top numbers are equal. Use the top numbers to order them.
Method. With the same denominator, the order is the order of the numerators.
- Look at the bottom numbers. They are all the same, so compare the top numbers only.All are 10ths
- Order the top numbers. Smallest top number first.5, 7, 8, 9
- Write the fractions in order. Put the fractions back in the same order.5/10, 7/10, 8/10, 9/10
Check. Check: the first fraction has the fewest parts, and the last has the most.
Watch out. The fractions are the same size if the top numbers are equal. Use the top numbers to order them.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 8. The denominator is multiplied by this number.2 × 4 = 8
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.1 × 4 = 4
- Write the equal fraction. The new fraction has the same value.4/8
Check. Check: 4/8 simplifies to 1/2.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. With the same denominator, compare the numerators.
- Look at the bottom numbers. Both fractions have the same bottom number, so the parts are the same size.Both are 4ths
- Compare the top numbers. With the same size of part, the bigger top number is the bigger fraction.1 and 2
- Choose the greater fraction. The fraction with more parts is greater.2/4
Check. Check: 2 parts is more than 1 parts of the same size.
Watch out. Do not compare the bottom numbers. The bigger the bottom number, the smaller each part.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 6. The denominator is multiplied by this number.3 × 2 = 6
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.2 × 2 = 4
- Write the equal fraction. The new fraction has the same value.4/6
Check. Check: 4/6 simplifies to 2/3.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 12. The denominator is multiplied by this number.3 × 4 = 12
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.1 × 4 = 4
- Write the equal fraction. The new fraction has the same value.4/12
Check. Check: 4/12 simplifies to 1/3.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. With the same denominator, compare the numerators.
- Look at the bottom numbers. Both fractions have the same bottom number, so the parts are the same size.Both are 4ths
- Compare the top numbers. With the same size of part, the bigger top number is the bigger fraction.3 and 2
- Choose the greater fraction. The fraction with more parts is greater.3/4
Check. Check: 3 parts is more than 2 parts of the same size.
Watch out. Do not compare the bottom numbers. The bigger the bottom number, the smaller each part.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 8. The denominator is multiplied by this number.4 × 2 = 8
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.2 × 2 = 4
- Write the equal fraction. The new fraction has the same value.4/8
Check. Check: 4/8 simplifies to 2/4.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. With the same denominator, the order is the order of the numerators.
- Look at the bottom numbers. They are all the same, so compare the top numbers only.All are 8ths
- Order the top numbers. Smallest top number first.3, 4, 6, 8
- Write the fractions in order. Put the fractions back in the same order.3/8, 4/8, 6/8, 8/8
Check. Check: the first fraction has the fewest parts, and the last has the most.
Watch out. The fractions are the same size if the top numbers are equal. Use the top numbers to order them.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 12. The denominator is multiplied by this number.4 × 3 = 12
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.2 × 3 = 6
- Write the equal fraction. The new fraction has the same value.6/12
Check. Check: 6/12 simplifies to 2/4.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. With the same denominator, compare the numerators.
- Look at the bottom numbers. Both fractions have the same bottom number, so the parts are the same size.Both are 4ths
- Compare the top numbers. With the same size of part, the bigger top number is the bigger fraction.1 and 3
- Choose the greater fraction. The fraction with more parts is greater.3/4
Check. Check: 3 parts is more than 1 parts of the same size.
Watch out. Do not compare the bottom numbers. The bigger the bottom number, the smaller each part.
Method. With the same denominator, the order is the order of the numerators.
- Look at the bottom numbers. They are all the same, so compare the top numbers only.All are 6ths
- Order the top numbers. Smallest top number first.2, 3, 4, 6
- Write the fractions in order. Put the fractions back in the same order.2/6, 3/6, 4/6, 6/6
Check. Check: the first fraction has the fewest parts, and the last has the most.
Watch out. The fractions are the same size if the top numbers are equal. Use the top numbers to order them.
Adding fractions with the same denominator
Add the top numbers. Keep the bottom number the same, because the parts are the same size: 2/8 + 3/8 = 5/8.
If the answer can be simplified, divide the top and bottom by the same number: 2/8 + 2/8 = 4/8 = 1/2.
Key ideas
- Add the top numbers; keep the bottom number.
- Simplify by dividing the top and bottom by the same number.
- Never add the bottom numbers.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 3 = 5
- Keep the bottom number 8. The total is counted in the same parts.5/8
- Write the answer. This is the simplest form.5/8
Check. Check: 5/8 is equal to 5/8.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 2 = 4
- Keep the bottom number 8. The total is counted in the same parts.4/8
- Simplify. Divide the top and bottom by the same number, which is 4.4/8 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 is equal to 4/8.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.3 + 4 = 7
- Keep the bottom number 10. The total is counted in the same parts.7/10
- Write the answer. This is the simplest form.7/10
Check. Check: 7/10 is equal to 7/10.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Watch out
Watch out. 2/8 + 3/8 is 5/8, not 5/16. The bottom number does not change when you add.
Exam tip
Grown-up tip. Ask the child: “Are the pieces the same size? If so, what changes when you add?”
Exercise 6B Practice: adding fractions
Non-calculatorMethod. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.5 + 1 = 6
- Keep the bottom number 8. The total is counted in the same parts.6/8
- Simplify. Divide the top and bottom by the same number, which is 2.6/8 = 3/4
- Write the answer. This is the simplest form.3/4
Check. Check: 3/4 is equal to 6/8.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 2 = 3
- Keep the bottom number 6. The total is counted in the same parts.3/6
- Simplify. Divide the top and bottom by the same number, which is 3.3/6 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 is equal to 3/6.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 2 = 4
- Keep the bottom number 5. The total is counted in the same parts.4/5
- Write the answer. This is the simplest form.4/5
Check. Check: 4/5 is equal to 4/5.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.3 + 1 = 4
- Keep the bottom number 6. The total is counted in the same parts.4/6
- Simplify. Divide the top and bottom by the same number, which is 2.4/6 = 2/3
- Write the answer. This is the simplest form.2/3
Check. Check: 2/3 is equal to 4/6.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.5 + 4 = 9
- Keep the bottom number 10. The total is counted in the same parts.9/10
- Write the answer. This is the simplest form.9/10
Check. Check: 9/10 is equal to 9/10.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 2 = 3
- Keep the bottom number 8. The total is counted in the same parts.3/8
- Write the answer. This is the simplest form.3/8
Check. Check: 3/8 is equal to 3/8.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.4 + 2 = 6
- Keep the bottom number 8. The total is counted in the same parts.6/8
- Simplify. Divide the top and bottom by the same number, which is 2.6/8 = 3/4
- Write the answer. This is the simplest form.3/4
Check. Check: 3/4 is equal to 6/8.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 1 = 3
- Keep the bottom number 4. The total is counted in the same parts.3/4
- Write the answer. This is the simplest form.3/4
Check. Check: 3/4 is equal to 3/4.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 1 = 2
- Keep the bottom number 4. The total is counted in the same parts.2/4
- Simplify. Divide the top and bottom by the same number, which is 2.2/4 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 is equal to 2/4.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.3 + 1 = 4
- Keep the bottom number 5. The total is counted in the same parts.4/5
- Write the answer. This is the simplest form.4/5
Check. Check: 4/5 is equal to 4/5.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 1 = 3
- Keep the bottom number 5. The total is counted in the same parts.3/5
- Write the answer. This is the simplest form.3/5
Check. Check: 3/5 is equal to 3/5.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 3 = 4
- Keep the bottom number 5. The total is counted in the same parts.4/5
- Write the answer. This is the simplest form.4/5
Check. Check: 4/5 is equal to 4/5.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 2 = 3
- Keep the bottom number 4. The total is counted in the same parts.3/4
- Write the answer. This is the simplest form.3/4
Check. Check: 3/4 is equal to 3/4.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.4 + 1 = 5
- Keep the bottom number 6. The total is counted in the same parts.5/6
- Write the answer. This is the simplest form.5/6
Check. Check: 5/6 is equal to 5/6.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 2 = 4
- Keep the bottom number 6. The total is counted in the same parts.4/6
- Simplify. Divide the top and bottom by the same number, which is 2.4/6 = 2/3
- Write the answer. This is the simplest form.2/3
Check. Check: 2/3 is equal to 4/6.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.6 + 1 = 7
- Keep the bottom number 10. The total is counted in the same parts.7/10
- Write the answer. This is the simplest form.7/10
Check. Check: 7/10 is equal to 7/10.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Subtracting fractions with the same denominator
Subtract the top numbers and keep the bottom number: 7/8 - 2/8 = 5/8.
Simplify the answer if you can: 6/8 - 2/8 = 4/8 = 1/2.
Key ideas
- Subtract the top numbers; keep the bottom number.
- Simplify the answer if you can.
- Check by adding back.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.7 - 2 = 5
- Keep the bottom number 8. The parts are the same size, so the bottom number does not change.5/8
- Write the answer. This is the simplest form.5/8
Check. Check: 5/8 + 2/8 gives 7/8.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.6 - 2 = 4
- Keep the bottom number 8. The parts are the same size, so the bottom number does not change.4/8
- Simplify. Divide the top and bottom by 4.4/8 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 + 2/8 gives 6/8.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.9 - 4 = 5
- Keep the bottom number 10. The parts are the same size, so the bottom number does not change.5/10
- Simplify. Divide the top and bottom by 5.5/10 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 + 4/10 gives 9/10.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Watch out
Watch out. 7/8 - 2/8 is 5/8. Do not write 5/6, and do not subtract the bottom numbers.
Exam tip
Grown-up tip. Use a bar cut into 8 parts. Take away 2 parts and count what is left.
Exercise 6C Practice: subtracting fractions
Non-calculatorMethod. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.2 - 1 = 1
- Keep the bottom number 5. The parts are the same size, so the bottom number does not change.1/5
- Write the answer. This is the simplest form.1/5
Check. Check: 1/5 + 1/5 gives 2/5.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.2 - 1 = 1
- Keep the bottom number 6. The parts are the same size, so the bottom number does not change.1/6
- Write the answer. This is the simplest form.1/6
Check. Check: 1/6 + 1/6 gives 2/6.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.4 - 2 = 2
- Keep the bottom number 5. The parts are the same size, so the bottom number does not change.2/5
- Write the answer. This is the simplest form.2/5
Check. Check: 2/5 + 2/5 gives 4/5.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.3 - 1 = 2
- Keep the bottom number 4. The parts are the same size, so the bottom number does not change.2/4
- Simplify. Divide the top and bottom by 2.2/4 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 + 1/4 gives 3/4.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.8 - 4 = 4
- Keep the bottom number 10. The parts are the same size, so the bottom number does not change.4/10
- Simplify. Divide the top and bottom by 2.4/10 = 2/5
- Write the answer. This is the simplest form.2/5
Check. Check: 2/5 + 4/10 gives 8/10.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.6 - 2 = 4
- Keep the bottom number 8. The parts are the same size, so the bottom number does not change.4/8
- Simplify. Divide the top and bottom by 4.4/8 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 + 2/8 gives 6/8.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.9 - 7 = 2
- Keep the bottom number 10. The parts are the same size, so the bottom number does not change.2/10
- Simplify. Divide the top and bottom by 2.2/10 = 1/5
- Write the answer. This is the simplest form.1/5
Check. Check: 1/5 + 7/10 gives 9/10.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.2 - 1 = 1
- Keep the bottom number 4. The parts are the same size, so the bottom number does not change.1/4
- Write the answer. This is the simplest form.1/4
Check. Check: 1/4 + 1/4 gives 2/4.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.5 - 2 = 3
- Keep the bottom number 6. The parts are the same size, so the bottom number does not change.3/6
- Simplify. Divide the top and bottom by 3.3/6 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 + 2/6 gives 5/6.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.3 - 2 = 1
- Keep the bottom number 4. The parts are the same size, so the bottom number does not change.1/4
- Write the answer. This is the simplest form.1/4
Check. Check: 1/4 + 2/4 gives 3/4.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.9 - 4 = 5
- Keep the bottom number 10. The parts are the same size, so the bottom number does not change.5/10
- Simplify. Divide the top and bottom by 5.5/10 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 + 4/10 gives 9/10.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.3 - 1 = 2
- Keep the bottom number 6. The parts are the same size, so the bottom number does not change.2/6
- Simplify. Divide the top and bottom by 2.2/6 = 1/3
- Write the answer. This is the simplest form.1/3
Check. Check: 1/3 + 1/6 gives 3/6.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.6 - 3 = 3
- Keep the bottom number 8. The parts are the same size, so the bottom number does not change.3/8
- Write the answer. This is the simplest form.3/8
Check. Check: 3/8 + 3/8 gives 6/8.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.4 - 1 = 3
- Keep the bottom number 5. The parts are the same size, so the bottom number does not change.3/5
- Write the answer. This is the simplest form.3/5
Check. Check: 3/5 + 1/5 gives 4/5.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.5 - 4 = 1
- Keep the bottom number 6. The parts are the same size, so the bottom number does not change.1/6
- Write the answer. This is the simplest form.1/6
Check. Check: 1/6 + 4/6 gives 5/6.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.4 - 3 = 1
- Keep the bottom number 6. The parts are the same size, so the bottom number does not change.1/6
- Write the answer. This is the simplest form.1/6
Check. Check: 1/6 + 3/6 gives 4/6.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Totals greater than one
When the top number is bigger than the bottom number, the total is more than one whole. 5/4 is 4/4 and 1/4, so it is 1 1/4.
Write the whole ones first, then the fraction that is left.
Key ideas
- A top number bigger than the bottom means more than one whole.
- Write the whole ones, then the fraction left over.
- Simplify the fraction part if you can.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 2 = 5
- Write the total. 5 parts of size 1/4.5/4
- Write as a mixed number. There are 1 whole one and 1/4 left over.5/4 = 1 1/4
- Write the answer. This is the answer in its simplest form.1 1/4
Check. Check: 1 1/4 is more than 1, as 5/4 is more than 4/4.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 4 = 7
- Write the total. 7 parts of size 1/5.7/5
- Write as a mixed number. There are 1 whole one and 2/5 left over.7/5 = 1 2/5
- Write the answer. This is the answer in its simplest form.1 2/5
Check. Check: 1 2/5 is more than 1, as 7/5 is more than 5/5.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.4 + 3 = 7
- Write the total. 7 parts of size 1/6.7/6
- Write as a mixed number. There are 1 whole one and 1/6 left over.7/6 = 1 1/6
- Write the answer. This is the answer in its simplest form.1 1/6
Check. Check: 1 1/6 is more than 1, as 7/6 is more than 6/6.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Watch out
Watch out. 5/4 is 1 1/4, not 5 and 4 as separate numbers. Count the whole ones first.
Exam tip
Grown-up tip. Use two bars cut into 4 parts. Ask: “How many full bars are shaded? How many parts are left?”
Exercise 6D Practice: totals greater than one
Non-calculatorMethod. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.2 + 2 = 4
- Write the total. 4 parts of size 1/3.4/3
- Write as a mixed number. There are 1 whole one and 1/3 left over.4/3 = 1 1/3
- Write the answer. This is the answer in its simplest form.1 1/3
Check. Check: 1 1/3 is more than 1, as 4/3 is more than 3/3.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.5 + 4 = 9
- Write the total. 9 parts of size 1/8.9/8
- Write as a mixed number. There are 1 whole one and 1/8 left over.9/8 = 1 1/8
- Write the answer. This is the answer in its simplest form.1 1/8
Check. Check: 1 1/8 is more than 1, as 9/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.4 + 4 = 8
- Write the total. 8 parts of size 1/6.8/6
- Write as a mixed number. There are 1 whole one and 1/3 left over.4/3 = 1 1/3
- Write the answer. This is the answer in its simplest form.1 1/3
Check. Check: 1 1/3 is more than 1, as 8/6 is more than 6/6.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.2 + 3 = 5
- Write the total. 5 parts of size 1/4.5/4
- Write as a mixed number. There are 1 whole one and 1/4 left over.5/4 = 1 1/4
- Write the answer. This is the answer in its simplest form.1 1/4
Check. Check: 1 1/4 is more than 1, as 5/4 is more than 4/4.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.2 + 4 = 6
- Write the total. 6 parts of size 1/5.6/5
- Write as a mixed number. There are 1 whole one and 1/5 left over.6/5 = 1 1/5
- Write the answer. This is the answer in its simplest form.1 1/5
Check. Check: 1 1/5 is more than 1, as 6/5 is more than 5/5.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.6 + 6 = 12
- Write the total. 12 parts of size 1/8.12/8
- Write as a mixed number. There are 1 whole one and 1/2 left over.3/2 = 1 1/2
- Write the answer. This is the answer in its simplest form.1 1/2
Check. Check: 1 1/2 is more than 1, as 12/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.4 + 3 = 7
- Write the total. 7 parts of size 1/6.7/6
- Write as a mixed number. There are 1 whole one and 1/6 left over.7/6 = 1 1/6
- Write the answer. This is the answer in its simplest form.1 1/6
Check. Check: 1 1/6 is more than 1, as 7/6 is more than 6/6.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 7 = 10
- Write the total. 10 parts of size 1/8.10/8
- Write as a mixed number. There are 1 whole one and 1/4 left over.5/4 = 1 1/4
- Write the answer. This is the answer in its simplest form.1 1/4
Check. Check: 1 1/4 is more than 1, as 10/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 4 = 7
- Write the total. 7 parts of size 1/5.7/5
- Write as a mixed number. There are 1 whole one and 2/5 left over.7/5 = 1 2/5
- Write the answer. This is the answer in its simplest form.1 2/5
Check. Check: 1 2/5 is more than 1, as 7/5 is more than 5/5.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.7 + 2 = 9
- Write the total. 9 parts of size 1/8.9/8
- Write as a mixed number. There are 1 whole one and 1/8 left over.9/8 = 1 1/8
- Write the answer. This is the answer in its simplest form.1 1/8
Check. Check: 1 1/8 is more than 1, as 9/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.4 + 3 = 7
- Write the total. 7 parts of size 1/5.7/5
- Write as a mixed number. There are 1 whole one and 2/5 left over.7/5 = 1 2/5
- Write the answer. This is the answer in its simplest form.1 2/5
Check. Check: 1 2/5 is more than 1, as 7/5 is more than 5/5.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.5 + 5 = 10
- Write the total. 10 parts of size 1/8.10/8
- Write as a mixed number. There are 1 whole one and 1/4 left over.5/4 = 1 1/4
- Write the answer. This is the answer in its simplest form.1 1/4
Check. Check: 1 1/4 is more than 1, as 10/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 2 = 5
- Write the total. 5 parts of size 1/4.5/4
- Write as a mixed number. There are 1 whole one and 1/4 left over.5/4 = 1 1/4
- Write the answer. This is the answer in its simplest form.1 1/4
Check. Check: 1 1/4 is more than 1, as 5/4 is more than 4/4.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.7 + 7 = 14
- Write the total. 14 parts of size 1/8.14/8
- Write as a mixed number. There are 1 whole one and 3/4 left over.7/4 = 1 3/4
- Write the answer. This is the answer in its simplest form.1 3/4
Check. Check: 1 3/4 is more than 1, as 14/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.4 + 5 = 9
- Write the total. 9 parts of size 1/6.9/6
- Write as a mixed number. There are 1 whole one and 1/2 left over.3/2 = 1 1/2
- Write the answer. This is the answer in its simplest form.1 1/2
Check. Check: 1 1/2 is more than 1, as 9/6 is more than 6/6.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 3 = 6
- Write the total. 6 parts of size 1/4.6/4
- Write as a mixed number. There are 1 whole one and 1/2 left over.3/2 = 1 1/2
- Write the answer. This is the answer in its simplest form.1 1/2
Check. Check: 1 1/2 is more than 1, as 6/4 is more than 4/4.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Fractions of lengths and amounts
To find a fraction of an amount, divide by the bottom number to find one part, then multiply by the top number.
For 3/5 of 60: 60 ÷ 5 = 12 for one fifth, and 3 × 12 = 36.
Key ideas
- Divide by the bottom number to find one part.
- Multiply by the top number to find the parts you want.
- Keep the unit from the question.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 5th of 60. Share 60 into 5 equal parts.60 ÷ 5 = 12
- Take 3 of those parts. The top number tells us how many parts.3 × 12 = 36
- Write the answer. Keep the unit from the question.36 cm
Check. Check: 12 × 5 = 60, and 3 parts is 36.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 8th of 48. Share 48 into 8 equal parts.48 ÷ 8 = 6
- Take 3 of those parts. The top number tells us how many parts.3 × 6 = 18
- Write the answer. Keep the unit from the question.18 cm
Check. Check: 6 × 8 = 48, and 3 parts is 18.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 5th of 35. Share 35 into 5 equal parts.35 ÷ 5 = 7
- Take 2 of those parts. The top number tells us how many parts.2 × 7 = 14
- Write the answer. Keep the unit from the question.14 cm
Check. Check: 7 × 5 = 35, and 2 parts is 14.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Watch out
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Exam tip
Grown-up tip. Ask: “How many equal parts is the whole split into? How many of those parts do we want?”
Exercise 6E Practice: fractions of lengths and amounts
Non-calculatorMethod. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 6th of 66. Share 66 into 6 equal parts.66 ÷ 6 = 11
- Take 5 of those parts. The top number tells us how many parts.5 × 11 = 55
- Write the answer. Keep the unit from the question.55 cm
Check. Check: 11 × 6 = 66, and 5 parts is 55.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 8th of 80. Share 80 into 8 equal parts.80 ÷ 8 = 10
- Take 6 of those parts. The top number tells us how many parts.6 × 10 = 60
- Write the answer. Keep the unit from the question.60 sweets
Check. Check: 10 × 8 = 80, and 6 parts is 60.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 5th of 10. Share 10 into 5 equal parts.10 ÷ 5 = 2
- Take 4 of those parts. The top number tells us how many parts.4 × 2 = 8
- Write the answer. Keep the unit from the question.8 sweets
Check. Check: 2 × 5 = 10, and 4 parts is 8.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 8th of 80. Share 80 into 8 equal parts.80 ÷ 8 = 10
- Take 4 of those parts. The top number tells us how many parts.4 × 10 = 40
- Write the answer. Keep the unit from the question.40 sweets
Check. Check: 10 × 8 = 80, and 4 parts is 40.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 5th of 35. Share 35 into 5 equal parts.35 ÷ 5 = 7
- Take 1 of those parts. The top number tells us how many parts.1 × 7 = 7
- Write the answer. Keep the unit from the question.7 sweets
Check. Check: 7 × 5 = 35, and 1 parts is 7.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 4th of 44. Share 44 into 4 equal parts.44 ÷ 4 = 11
- Take 3 of those parts. The top number tells us how many parts.3 × 11 = 33
- Write the answer. Keep the unit from the question.33 sweets
Check. Check: 11 × 4 = 44, and 3 parts is 33.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 6th of 30. Share 30 into 6 equal parts.30 ÷ 6 = 5
- Take 2 of those parts. The top number tells us how many parts.2 × 5 = 10
- Write the answer. Keep the unit from the question.10 cm
Check. Check: 5 × 6 = 30, and 2 parts is 10.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 10th of 50. Share 50 into 10 equal parts.50 ÷ 10 = 5
- Take 8 of those parts. The top number tells us how many parts.8 × 5 = 40
- Write the answer. Keep the unit from the question.40 sweets
Check. Check: 5 × 10 = 50, and 8 parts is 40.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 10th of 20. Share 20 into 10 equal parts.20 ÷ 10 = 2
- Take 1 of those parts. The top number tells us how many parts.1 × 2 = 2
- Write the answer. Keep the unit from the question.2 sweets
Check. Check: 2 × 10 = 20, and 1 parts is 2.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 10th of 30. Share 30 into 10 equal parts.30 ÷ 10 = 3
- Take 3 of those parts. The top number tells us how many parts.3 × 3 = 9
- Write the answer. Keep the unit from the question.9 cm
Check. Check: 3 × 10 = 30, and 3 parts is 9.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 8th of 16. Share 16 into 8 equal parts.16 ÷ 8 = 2
- Take 3 of those parts. The top number tells us how many parts.3 × 2 = 6
- Write the answer. Keep the unit from the question.6 sweets
Check. Check: 2 × 8 = 16, and 3 parts is 6.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 6th of 36. Share 36 into 6 equal parts.36 ÷ 6 = 6
- Take 3 of those parts. The top number tells us how many parts.3 × 6 = 18
- Write the answer. Keep the unit from the question.18 cm
Check. Check: 6 × 6 = 36, and 3 parts is 18.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 6th of 66. Share 66 into 6 equal parts.66 ÷ 6 = 11
- Take 1 of those parts. The top number tells us how many parts.1 × 11 = 11
- Write the answer. Keep the unit from the question.11 cm
Check. Check: 11 × 6 = 66, and 1 parts is 11.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 5th of 45. Share 45 into 5 equal parts.45 ÷ 5 = 9
- Take 1 of those parts. The top number tells us how many parts.1 × 9 = 9
- Write the answer. Keep the unit from the question.9 cm
Check. Check: 9 × 5 = 45, and 1 parts is 9.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 4th of 20. Share 20 into 4 equal parts.20 ÷ 4 = 5
- Take 2 of those parts. The top number tells us how many parts.2 × 5 = 10
- Write the answer. Keep the unit from the question.10 sweets
Check. Check: 5 × 4 = 20, and 2 parts is 10.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 3th of 24. Share 24 into 3 equal parts.24 ÷ 3 = 8
- Take 2 of those parts. The top number tells us how many parts.2 × 8 = 16
- Write the answer. Keep the unit from the question.16 sweets
Check. Check: 8 × 3 = 24, and 2 parts is 16.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Chapter summary
| Skill | Method |
|---|---|
| Same denominator | Compare and order by the top numbers; the parts are the same size |
| Equal fractions | Multiply the top and bottom by the same number |
| Adding and subtracting | Add or subtract the top numbers; keep the bottom number; simplify |
| Totals over one | Write the whole ones, then the fraction left: 5/4 = 1 1/4 |
| Fractions of amounts | Divide by the bottom number, then multiply by the top number |
Can you…?
- I can compare and order fractions with the same denominator
- I can write an equal fraction with a small denominator, using a diagram
- I can add and subtract fractions with the same denominator, and simplify
- I can write a total greater than one as a mixed number
- I can find a fraction of a length or an amount
Key terms
- numerator
- the top number of a fraction
- denominator
- the bottom number of a fraction
- simplify
- divide the top and bottom by the same number to make a fraction smaller
- mixed number
- a whole number and a fraction, such as 1 1/4
Exercise 6Z Check-up
Non-calculatorMethod. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 3 = 5
- Keep the bottom number 6. The total is counted in the same parts.5/6
- Write the answer. This is the simplest form.5/6
Check. Check: 5/6 is equal to 5/6.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.4 + 4 = 8
- Write the total. 8 parts of size 1/5.8/5
- Write as a mixed number. There are 1 whole one and 3/5 left over.8/5 = 1 3/5
- Write the answer. This is the answer in its simplest form.1 3/5
Check. Check: 1 3/5 is more than 1, as 8/5 is more than 5/5.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.7 - 4 = 3
- Keep the bottom number 10. The parts are the same size, so the bottom number does not change.3/10
- Write the answer. This is the simplest form.3/10
Check. Check: 3/10 + 4/10 gives 7/10.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 3 = 4
- Keep the bottom number 5. The total is counted in the same parts.4/5
- Write the answer. This is the simplest form.4/5
Check. Check: 4/5 is equal to 4/5.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 3 = 4
- Keep the bottom number 6. The total is counted in the same parts.4/6
- Simplify. Divide the top and bottom by the same number, which is 2.4/6 = 2/3
- Write the answer. This is the simplest form.2/3
Check. Check: 2/3 is equal to 4/6.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.7 + 7 = 14
- Write the total. 14 parts of size 1/8.14/8
- Write as a mixed number. There are 1 whole one and 3/4 left over.7/4 = 1 3/4
- Write the answer. This is the answer in its simplest form.1 3/4
Check. Check: 1 3/4 is more than 1, as 14/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. With the same denominator, the order is the order of the numerators.
- Look at the bottom numbers. They are all the same, so compare the top numbers only.All are 10ths
- Order the top numbers. Smallest top number first.2, 5, 6, 10
- Write the fractions in order. Put the fractions back in the same order.2/10, 5/10, 6/10, 10/10
Check. Check: the first fraction has the fewest parts, and the last has the most.
Watch out. The fractions are the same size if the top numbers are equal. Use the top numbers to order them.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 10th of 90. Share 90 into 10 equal parts.90 ÷ 10 = 9
- Take 9 of those parts. The top number tells us how many parts.9 × 9 = 81
- Write the answer. Keep the unit from the question.81 sweets
Check. Check: 9 × 10 = 90, and 9 parts is 81.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Multiply the top and bottom by the same number. The fraction stays the same size.
- Find how many times the bottom number goes into 8. The denominator is multiplied by this number.4 × 2 = 8
- Multiply the top number by the same number. Do the same to the top and bottom, so the fraction stays equal.3 × 2 = 6
- Write the equal fraction. The new fraction has the same value.6/8
Check. Check: 6/8 simplifies to 3/4.
Watch out. Multiply the top and the bottom. Do not add the same number to each.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.7 + 4 = 11
- Write the total. 11 parts of size 1/8.11/8
- Write as a mixed number. There are 1 whole one and 3/8 left over.11/8 = 1 3/8
- Write the answer. This is the answer in its simplest form.1 3/8
Check. Check: 1 3/8 is more than 1, as 11/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Total 19 marks. Allow about 19 minutes.
Exercise 6X Practice test questions
Non-calculatorMethod. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.3 - 1 = 2
- Keep the bottom number 5. The parts are the same size, so the bottom number does not change.2/5
- Write the answer. This is the simplest form.2/5
Check. Check: 2/5 + 1/5 gives 3/5.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 4th of 8. Share 8 into 4 equal parts.8 ÷ 4 = 2
- Take 3 of those parts. The top number tells us how many parts.3 × 2 = 6
- Write the answer. Keep the unit from the question.6 cm
Check. Check: 2 × 4 = 8, and 3 parts is 6.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 1 = 3
- Keep the bottom number 4. The total is counted in the same parts.3/4
- Write the answer. This is the simplest form.3/4
Check. Check: 3/4 is equal to 3/4.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.4 - 2 = 2
- Keep the bottom number 8. The parts are the same size, so the bottom number does not change.2/8
- Simplify. Divide the top and bottom by 2.2/8 = 1/4
- Write the answer. This is the simplest form.1/4
Check. Check: 1/4 + 2/8 gives 4/8.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.
Method. Divide by the bottom number to find one part, then multiply by the top number.
- Find one 8th of 32. Share 32 into 8 equal parts.32 ÷ 8 = 4
- Take 1 of those parts. The top number tells us how many parts.1 × 4 = 4
- Write the answer. Keep the unit from the question.4 sweets
Check. Check: 4 × 8 = 32, and 1 parts is 4.
Watch out. Divide first, then multiply. Do not multiply by the bottom number.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.1 + 4 = 5
- Keep the bottom number 10. The total is counted in the same parts.5/10
- Simplify. Divide the top and bottom by the same number, which is 5.5/10 = 1/2
- Write the answer. This is the simplest form.1/2
Check. Check: 1/2 is equal to 5/10.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.7 + 7 = 14
- Write the total. 14 parts of size 1/8.14/8
- Write as a mixed number. There are 1 whole one and 3/4 left over.7/4 = 1 3/4
- Write the answer. This is the answer in its simplest form.1 3/4
Check. Check: 1 3/4 is more than 1, as 14/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. Add the top numbers and keep the bottom number. Simplify if you can.
- Add the top numbers. The bottom number stays the same, because the parts are the same size.2 + 1 = 3
- Keep the bottom number 10. The total is counted in the same parts.3/10
- Write the answer. This is the simplest form.3/10
Check. Check: 3/10 is equal to 3/10.
Watch out. Do not add the bottom numbers too. 2/8 + 3/8 is 5/8, not 5/16.
Method. More than one whole: add the top numbers, then write the whole ones out.
- Add the top numbers. Keep the bottom number the same.3 + 7 = 10
- Write the total. 10 parts of size 1/8.10/8
- Write as a mixed number. There are 1 whole one and 1/4 left over.5/4 = 1 1/4
- Write the answer. This is the answer in its simplest form.1 1/4
Check. Check: 1 1/4 is more than 1, as 10/8 is more than 8/8.
Watch out. A top number bigger than the bottom is more than one whole. Write it as a mixed number.
Method. Subtract the top numbers and keep the bottom number. Simplify if you can.
- Subtract the top numbers. The bottom number stays the same.8 - 4 = 4
- Keep the bottom number 10. The parts are the same size, so the bottom number does not change.4/10
- Simplify. Divide the top and bottom by 2.4/10 = 2/5
- Write the answer. This is the simplest form.2/5
Check. Check: 2/5 + 4/10 gives 8/10.
Watch out. Do not subtract the bottom numbers. 7/8 - 3/8 is 4/8, which is 1/2.