Fractions
By the end of this chapter you will be able to
- Simplify a fraction by dividing by a common factor
- Find equivalent fractions and compare fractions with different denominators
- Convert between mixed numbers and improper fractions
- Add and subtract fractions, including mixed numbers
- Multiply and divide fractions, and write a fraction as a decimal
You should already know
- Equivalent fractions and simple fractions of amounts (Year 4 and 5 maths)
- Common multiples and factors (Year 5 maths)
Where this leads
- Decimals and percentages, including fractions as percentages (Chapter 4 of this book)
KS2 SATs practice for arithmetic (Year 6). Original questions in the style of the national tests. Content: Compare and order fractions, including fractions greater than 1 (Year 5-6), Identify, name and write equivalent fractions, and use common factors to simplify (Year 5-6), Recognise mixed numbers and improper fractions, and convert between them (Year 5), Add and subtract fractions with the same denominator or with denominators that are multiples of the same number (Year 5), Add and subtract fractions with different denominators and mixed numbers, using equivalent fractions and common multiples (Year 6), Multiply proper fractions and mixed numbers by whole numbers (Year 5); multiply simple pairs of proper fractions in simplest form (Year 6), Divide proper fractions by whole numbers; associate a fraction with division and find decimal equivalents (Year 6).
Exercise P Do you remember?
Non-calculatorMethod. Divide the whole by 3.
- Divide by the bottom number. 27 ÷ 3 = 9.27 ÷ 3 = 9
- Write the answer. 9
Check. 1/3 of 27 is 9, because 3 × 9 = 27. ✓
Method. Find one quarter, then multiply by three.
- Find one quarter. 12 ÷ 4 = 3.3
- Multiply by 3. 3 × 3 = 9.9
- Write the answer. 9
Check. 9 is three quarters of 12. ✓
Method. Test each choice against the question.
- Read what the question asks. Decide what you need to find or check.
- Test the choice. Four eighths is the same as half, since 4 × 2 = 8 and 1 × 4 = 4.4/8 is right
- Reject the other choices. 2/5 and 3/4 are not half of their wholes.2/5 and 3/4 are not right
- Write the answer. 4/8
Check. 4/8 is right. ✓
Method. The bottoms are the same, so add the tops.
- Add the tops. 2 + 1 = 3.3
- Keep the bottom. The bottom stays 5.3/5
- Write the answer. 3/5
Check. 3/5 is the same as 1/5 + 1/5 + 1/5. ✓
Method. Use a times table fact.
- Recall the fact. Five fours are twenty.5 × 4 = 20
- Write the answer. 20
Check. 4 × 5 = 20 as well. ✓
Equivalent fractions and simplifying
Rule
Equivalent fractions have the same value but different numbers. Multiply the top and the bottom by the same number to make an equivalent fraction.
To simplify, divide the top and bottom by a common factor. A fraction is in its simplest form when no number divides into both except 1.
For the full explanation, read Year 6 maths, chapter 2.
Key ideas
- Multiply or divide the top and bottom by the same number to get an equivalent fraction.
- The highest common factor (HCF) gives the simplest form in one step.
- Check a simplified fraction by seeing whether the top and bottom still share a factor.
Method. Find the highest common factor of the top and bottom, then divide both by it.
- Find a number that divides into both the top and the bottom. The highest common factor of 36 and 48 is 12.HCF of 36 and 48 is 12
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.36 ÷ 12 = 3, 48 ÷ 12 = 4
- Write the answer. 3/4
Check. 3 × 12 = 36 and 4 × 12 = 48, so 3/4 is the same fraction. ✓
Watch out. Dividing by 2 only gives 18/24, which can still be simplified.
Method. Find what 5 is multiplied by to make 20, then do the same to the top.
- Multiply the top and the bottom by the same number. Both are multiplied by 4, so the value of the fraction does not change.3 × 4 = 12 and 5 × 4 = 20
- Check the bottom. 5 × 4 = 20, which is the new bottom number.5 × 4 = 20
- Write the answer. 3/5
Check. 20 ÷ 5 = 4, so the top is 3 × 4 = 12. ✓
Method. Multiply the bottom by 5, and do the same to the top.
- Multiply the top and the bottom by the same number. Both are multiplied by 5, so the value of the fraction does not change.5 × 5 = 25 and 8 × 5 = 40
- Check the bottom. 8 × 5 = 40, which is the new bottom number.8 × 5 = 40
- Write the answer. 5/8
Check. 40 ÷ 8 = 5, so the top is 5 × 5 = 25. ✓
Exercise 3A Practice: equivalent fractions and simplifying
Non-calculatorMethod. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 12 and 18 is 6.HCF of 12 and 18 is 6
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.12 ÷ 6 = 2, 18 ÷ 6 = 3
- Write the answer. 2/3
Check. 2/3 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 45 and 60 is 15.HCF of 45 and 60 is 15
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.45 ÷ 15 = 3, 60 ÷ 15 = 4
- Write the answer. 3/4
Check. 3/4 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 28 and 42 is 14.HCF of 28 and 42 is 14
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.28 ÷ 14 = 2, 42 ÷ 14 = 3
- Write the answer. 2/3
Check. 2/3 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 16 and 40 is 8.HCF of 16 and 40 is 8
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.16 ÷ 8 = 2, 40 ÷ 8 = 5
- Write the answer. 2/5
Check. 2/5 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 36 and 54 is 18.HCF of 36 and 54 is 18
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.36 ÷ 18 = 2, 54 ÷ 18 = 3
- Write the answer. 2/3
Check. 2/3 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 24 and 30 is 6.HCF of 24 and 30 is 6
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.24 ÷ 6 = 4, 30 ÷ 6 = 5
- Write the answer. 4/5
Check. 4/5 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 56 and 72 is 8.HCF of 56 and 72 is 8
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.56 ÷ 8 = 7, 72 ÷ 8 = 9
- Write the answer. 7/9
Check. 7/9 is in simplest form, because no number divides into both. ✓
Method. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 9 and 27 is 9.HCF of 9 and 27 is 9
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.9 ÷ 9 = 1, 27 ÷ 9 = 3
- Write the answer. 1/3
Check. 1/3 is in simplest form, because no number divides into both. ✓
Method. Multiply the top and bottom by 5.
- Multiply the top and the bottom by the same number. Both are multiplied by 5, so the value of the fraction does not change.3 × 5 = 15 and 4 × 5 = 20
- Write the answer. 3/4
Check. 3/4 = 3/4 because 15/20 = 0.75 = 3/4. ✓
Method. Multiply the top and bottom by 5.
- Multiply the top and the bottom by the same number. Both are multiplied by 5, so the value of the fraction does not change.2 × 5 = 10 and 7 × 5 = 35
- Write the answer. 2/7
Check. 10/35 simplifies to 2/7, the same fraction. ✓
Method. Multiply the bottom by 4, and do the same to the top.
- Multiply the top and the bottom by the same number. Both are multiplied by 4, so the value of the fraction does not change.4 × 4 = 16 and 9 × 4 = 36
- Write the answer. 4/9
Check. 16/36 simplifies back to 4/9. ✓
Method. Simplify 6/12.
- Find a number that divides into both the top and the bottom. The highest common factor of 6 and 12 is 6.HCF of 6 and 12 is 6
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.6 ÷ 6 = 1, 12 ÷ 6 = 2
- Write the answer. 1/2
Check. Half the pizza is 6 slices. ✓
Method. Find the highest common factor of 35 and 49.
- Find a number that divides into both the top and the bottom. The highest common factor of 35 and 49 is 7.HCF of 35 and 49 is 7
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.35 ÷ 7 = 5, 49 ÷ 7 = 7
- Write the answer. 5/7
Check. 35 ÷ 7 = 5 and 49 ÷ 7 = 7, so 5/7. ✓
Method. Simplify 5/10 by dividing by the common factor.
- Find the common factor. Both 5 and 10 divide by 5.5 and 10 ÷ 5
- Divide. 5 ÷ 5 = 1 and 10 ÷ 5 = 2, so 5/10 = 1/2.5/10 = 1/2
- Write the answer. No, 5/10 is equal to 1/2 because 5/10 divided by 5 on top and bottom is 1/2.
Check. 1/2 = 0.5 and 5/10 = 0.5. ✓
Comparing and ordering fractions
Rule
To compare fractions, write them with the same denominator. The fraction with the bigger top number is bigger, when the bottoms are the same.
Fractions greater than 1 work the same way: 7/4 is bigger than 5/3 once both are written with 12 as the denominator.
Key ideas
- Write the fractions with a common denominator, then compare the tops.
- The bigger the top for the same bottom, the bigger the fraction.
- Fractions greater than 1 can be compared the same way.
Method. Write both fractions with the same denominator, then compare.
- Find a common denominator. 4 and 8 both divide into 8.8
- Write both fractions with that denominator. Multiply each top and bottom by the same number.3/4 = 6/8 and 5/8 = 5/8
- Compare the top numbers. 6 and 5 tell us which fraction is bigger.6 > 5, so 3/4 > 5/8
- Write the answer. >
Check. 3/4 = 6/8, which is bigger than 5/8. ✓
Watch out. Compare the tops only after the bottoms are equal.
Method. Use the common denominator 12 for both.
- Find a common denominator. 4 and 3 both divide into 12.12
- Write both fractions with that denominator. Multiply each top and bottom by the same number.7/4 = 21/12 and 5/3 = 20/12
- Compare the top numbers. 21 and 20 tell us which fraction is bigger.21 > 20, so 7/4 > 5/3
- Write the answer. >
Check. 7/4 = 1 3/4 and 5/3 = 1 2/3, and 1 3/4 is bigger. ✓
Method. Write each fraction with the denominator 12, then order the tops.
- Write with denominator 12. 5/6 = 10/12, 2/3 = 8/12 and 7/12 stays the same.10/12, 8/12, 7/12
- Order the tops from smallest. 7 is smallest, then 8, then 10.7/12 < 8/12 < 10/12
- Write the original fractions. Put back the original fractions in the same order.7/12, 2/3, 5/6
- Write the answer. 7/12, 2/3, 5/6
Check. The order is 7/12 (0.58), 2/3 (0.67), 5/6 (0.83). ✓
Exercise 3B Practice: comparing and ordering
Non-calculatorMethod. Write both with the same denominator.
- Find a common denominator. 4 and 8 both divide into 8.8
- Write both fractions with that denominator. Multiply each top and bottom by the same number.3/4 = 6/8 and 5/8 = 5/8
- Compare the top numbers. 6 and 5 tell us which fraction is bigger.6 > 5, so 3/4 > 5/8
- Write the answer. >
Check. The bigger fraction has the bigger top after this step. ✓
Method. Write both with the same denominator.
- Find a common denominator. 3 and 5 both divide into 15.15
- Write both fractions with that denominator. Multiply each top and bottom by the same number.2/3 = 10/15 and 3/5 = 9/15
- Compare the top numbers. 10 and 9 tell us which fraction is bigger.10 > 9, so 2/3 > 3/5
- Write the answer. >
Check. The bigger fraction has the bigger top after this step. ✓
Method. Write both with the same denominator.
- Find a common denominator. 10 and 4 both divide into 20.20
- Write both fractions with that denominator. Multiply each top and bottom by the same number.7/10 = 14/20 and 3/4 = 15/20
- Compare the top numbers. 14 and 15 tell us which fraction is bigger.14 < 15, so 7/10 < 3/4
- Write the answer. <
Check. The bigger fraction has the bigger top after this step. ✓
Method. Write both with the same denominator.
- Find a common denominator. 6 and 9 both divide into 18.18
- Write both fractions with that denominator. Multiply each top and bottom by the same number.5/6 = 15/18 and 7/9 = 14/18
- Compare the top numbers. 15 and 14 tell us which fraction is bigger.15 > 14, so 5/6 > 7/9
- Write the answer. >
Check. The bigger fraction has the bigger top after this step. ✓
Method. Write both with the same denominator.
- Find a common denominator. 5 and 11 both divide into 55.55
- Write both fractions with that denominator. Multiply each top and bottom by the same number.4/5 = 44/55 and 9/11 = 45/55
- Compare the top numbers. 44 and 45 tell us which fraction is bigger.44 < 45, so 4/5 < 9/11
- Write the answer. <
Check. The bigger fraction has the bigger top after this step. ✓
Method. Write both with the same denominator.
- Find a common denominator. 2 and 9 both divide into 18.18
- Write both fractions with that denominator. Multiply each top and bottom by the same number.1/2 = 9/18 and 4/9 = 8/18
- Compare the top numbers. 9 and 8 tell us which fraction is bigger.9 > 8, so 1/2 > 4/9
- Write the answer. >
Check. The bigger fraction has the bigger top after this step. ✓
Method. Both fractions are greater than 1; use the denominator 12.
- Find a common denominator. 4 and 3 both divide into 12.12
- Write both fractions with that denominator. Multiply each top and bottom by the same number.7/4 = 21/12 and 5/3 = 20/12
- Compare the top numbers. 21 and 20 tell us which fraction is bigger.21 > 20, so 7/4 > 5/3
- Write the answer. >
Check. 7/4 = 1 3/4 and 5/3 = 1 2/3. ✓
Method. Write each fraction with the denominator 8.
- Write with denominator 8. 3/4 = 6/8, 5/8 stays, 1/2 = 4/8.6/8, 5/8, 4/8
- Order the tops from largest. 6 is biggest, then 5, then 4.6/8 > 5/8 > 4/8
- Write the answer. 3/4, 5/8, 1/2
Check. 3/4 is 0.75, 5/8 is 0.625 and 1/2 is 0.5. ✓
Method. Use the common denominator 24.
- Write with denominator 24. 7/8 = 21/24 and 11/12 = 22/24.21/24 and 22/24
- Compare. 22 is bigger than 21.11/12 > 7/8
- Write the answer. 11/12
Check. 7/8 = 0.875 and 11/12 = 0.917. ✓
Method. Use the denominator 12 for both.
- Find a common denominator. 4 and 3 both divide into 12.12
- Write both fractions with that denominator. Multiply each top and bottom by the same number.9/4 = 27/12 and 7/3 = 28/12
- Compare the top numbers. 27 and 28 tell us which fraction is bigger.27 < 28, so 9/4 < 7/3
- Write the answer. <
Check. 9/4 = 2 1/4 and 7/3 = 2 1/3. ✓
Method. Look at the size of each piece, not the number of pieces.
- Write both with denominator 6. 1/3 = 2/6 and 1/2 = 3/6.2/6 and 3/6
- Compare. 3/6 is bigger than 2/6, so 1/2 is bigger.1/2 > 1/3
- Write the answer. No, 1/2 is greater, because a bigger bottom means smaller pieces.
Check. 0.5 is greater than 0.33. ✓
Mixed numbers and improper fractions
Rule
A mixed number has a whole number and a fraction, such as 2 3/4. An improper fraction has a top number that is bigger than its bottom number, such as 11/4.
To change a mixed number to an improper fraction: multiply the whole number by the bottom, add the top, and keep the bottom. To change back, divide the top by the bottom.
Key ideas
- 2 3/4 = 11/4, because 2 × 4 + 3 = 11.
- 17/5 = 3 2/5, because 17 ÷ 5 = 3 remainder 2.
- An improper fraction has a top number bigger than its bottom number.
Method. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 4 parts, so 2 wholes have 2 × 4 parts.2 × 4 = 8
- Add the top number. Add the 3 parts that are left over.8 + 3 = 11
- Keep the same bottom number. The size of each part does not change.11/4
- Write the answer. 11/4
Check. 11/4 = 2 3/4, because 4 × 2 = 8 and 8 + 3 = 11. ✓
Method. Divide the top by the bottom: the whole number and the remainder make the mixed number.
- Divide the top number by the bottom number. 17 ÷ 5 = 3 with 2 left over.17 ÷ 5 = 3 r 2
- Write the answer as a mixed number. The whole number is 3, and the 2 left over goes over 5.3 2/5
- Write the answer. 3 2/5
Check. 3 × 5 + 2 = 17. ✓
Watch out. The remainder goes on top of the same bottom: 2/5, not 2/3.
Method. Change the mixed number to an improper fraction, then compare.
- The bottom numbers are the same. So compare the top numbers.7/3 and 7/3
- Compare the top numbers. 7 and 7 tell us which fraction is bigger.7 = 7, so 7/3 = 7/3
- Write the answer. =
Check. 2 1/3 = 7/3. ✓
Exercise 3C Practice: mixed numbers and improper fractions
Non-calculatorMethod. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 3 parts, so 1 wholes have 1 × 3 parts.1 × 3 = 3
- Add the top number. Add the 2 parts that are left over.3 + 2 = 5
- Keep the same bottom number. The size of each part does not change.5/3
- Write the answer. 5/3
Check. 5/3 = 1 2/3, because 1 × 3 + 2 = 5. ✓
Method. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 2 parts, so 3 wholes have 3 × 2 parts.3 × 2 = 6
- Add the top number. Add the 1 parts that are left over.6 + 1 = 7
- Keep the same bottom number. The size of each part does not change.7/2
- Write the answer. 7/2
Check. 7/2 = 3 1/2, because 3 × 2 + 1 = 7. ✓
Method. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 8 parts, so 2 wholes have 2 × 8 parts.2 × 8 = 16
- Add the top number. Add the 3 parts that are left over.16 + 3 = 19
- Keep the same bottom number. The size of each part does not change.19/8
- Write the answer. 19/8
Check. 19/8 = 2 3/8, because 2 × 8 + 3 = 19. ✓
Method. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 4 parts, so 5 wholes have 5 × 4 parts.5 × 4 = 20
- Add the top number. Add the 1 parts that are left over.20 + 1 = 21
- Keep the same bottom number. The size of each part does not change.21/4
- Write the answer. 21/4
Check. 21/4 = 5 1/4, because 5 × 4 + 1 = 21. ✓
Method. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 5 parts, so 4 wholes have 4 × 5 parts.4 × 5 = 20
- Add the top number. Add the 3 parts that are left over.20 + 3 = 23
- Keep the same bottom number. The size of each part does not change.23/5
- Write the answer. 23/5
Check. 23/5 = 4 3/5, because 4 × 5 + 3 = 23. ✓
Method. Multiply the whole number by the bottom, then add the top.
- Multiply the whole number by the bottom number. Each whole has 6 parts, so 2 wholes have 2 × 6 parts.2 × 6 = 12
- Add the top number. Add the 1 parts that are left over.12 + 1 = 13
- Keep the same bottom number. The size of each part does not change.13/6
- Write the answer. 13/6
Check. 13/6 = 2 1/6, because 2 × 6 + 1 = 13. ✓
Method. Divide the top by the bottom.
- Divide the top number by the bottom number. 11 ÷ 4 = 2 with 3 left over.11 ÷ 4 = 2 r 3
- Write the answer as a mixed number. The whole number is 2, and the 3 left over goes over 4.2 3/4
- Write the answer. 2 3/4
Check. 2 3/4, because the whole number times 4 plus the remainder is 11. ✓
Method. Divide the top by the bottom.
- Divide the top number by the bottom number. 17 ÷ 6 = 2 with 5 left over.17 ÷ 6 = 2 r 5
- Write the answer as a mixed number. The whole number is 2, and the 5 left over goes over 6.2 5/6
- Write the answer. 2 5/6
Check. 2 5/6, because the whole number times 6 plus the remainder is 17. ✓
Method. Divide the top by the bottom.
- Divide the top number by the bottom number. 23 ÷ 5 = 4 with 3 left over.23 ÷ 5 = 4 r 3
- Write the answer as a mixed number. The whole number is 4, and the 3 left over goes over 5.4 3/5
- Write the answer. 4 3/5
Check. 4 3/5, because the whole number times 5 plus the remainder is 23. ✓
Method. Divide the top by the bottom.
- Divide the top number by the bottom number. 14 ÷ 3 = 4 with 2 left over.14 ÷ 3 = 4 r 2
- Write the answer as a mixed number. The whole number is 4, and the 2 left over goes over 3.4 2/3
- Write the answer. 4 2/3
Check. 4 2/3, because the whole number times 3 plus the remainder is 14. ✓
Method. Divide the top by the bottom.
- Divide the top number by the bottom number. 19 ÷ 8 = 2 with 3 left over.19 ÷ 8 = 2 r 3
- Write the answer as a mixed number. The whole number is 2, and the 3 left over goes over 8.2 3/8
- Write the answer. 2 3/8
Check. 2 3/8, because the whole number times 8 plus the remainder is 19. ✓
Method. Change 4 3/8 to an improper fraction.
- Multiply the whole number by the bottom number. Each whole has 8 parts, so 4 wholes have 4 × 8 parts.4 × 8 = 32
- Add the top number. Add the 3 parts that are left over.32 + 3 = 35
- Keep the same bottom number. The size of each part does not change.35/8
- Write the answer. 35/8
Check. 35/8 = 4 3/8, and 35 ÷ 8 = 4 remainder 3. ✓
Method. Divide 50 by 7 and write the remainder over 7.
- Divide the top number by the bottom number. 50 ÷ 7 = 7 with 1 left over.50 ÷ 7 = 7 r 1
- Write the answer as a mixed number. The whole number is 7, and the 1 left over goes over 7.7 1/7
- Write the answer. 7 1/7
Check. 7 × 7 + 1 = 50, so 50/7 = 7 1/7. ✓
Method. Divide 9 by 4 and read the answer as wholes and parts.
- Divide. 9 ÷ 4 = 2 remainder 1.9 ÷ 4 = 2 r 1
- Read the answer. Two wholes and one quarter left over.2 1/4
- Write the answer. 9/4 means 9 quarters; 4 quarters make one whole, so 9 quarters is 2 wholes and 1 quarter.
Check. 2 × 4 + 1 = 9. ✓
Method. Divide 13 by 4.
- Divide the top number by the bottom number. 13 ÷ 4 = 3 with 1 left over.13 ÷ 4 = 3 r 1
- Write the answer as a mixed number. The whole number is 3, and the 1 left over goes over 4.3 1/4
- Write the answer. 3 1/4
Check. 3 × 4 + 1 = 13. ✓
Method. Multiply the whole number by 5, add 2, and keep the bottom.
- Multiply the whole number by the bottom number. Each whole has 5 parts, so 3 wholes have 3 × 5 parts.3 × 5 = 15
- Add the top number. Add the 2 parts that are left over.15 + 2 = 17
- Keep the same bottom number. The size of each part does not change.17/5
- Write the answer. 17/5
Check. 3 × 5 + 2 = 17. ✓
Adding and subtracting fractions
Rule
If the bottoms are the same, add or subtract the tops and keep the bottom.
If the bottoms are different, first write both fractions with a common denominator, which is a common multiple of the bottoms. Then add or subtract the tops.
Key ideas
- Same bottom: add or subtract the tops only.
- Different bottoms: find a common multiple, make equivalent fractions, then add or subtract.
- Give the answer in its simplest form, and as a mixed number if the answer is bigger than 1.
Method. The bottoms are the same, so add the tops.
- The bottom numbers are the same. So add the top numbers and keep the bottom number.2 + 3 = 5, so 5/7
- Write the answer. The fraction cannot be simplified.5/7
- Write the answer. 5/7
Check. 5/7 is less than one whole, so the answer is sensible. ✓
Method. Find a common denominator of 4 and 5, which is 20.
- Find a common denominator. 4 and 5 both divide into 20.20
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.3/4 = 15/20 and 2/5 = 8/20
- Add the top numbers. The bottom number stays the same.15 + 8 = 23, so 23/20
- Write the answer. The fraction cannot be simplified.23/20
- Write the answer as a mixed number. 23 ÷ 20 = 1 remainder 3.23/20 = 1 3/20
- Write the answer. 1 3/20
Check. 15/20 + 8/20 = 23/20 = 1 3/20. ✓
Method. Find a common denominator of 6 and 4, which is 12.
- Find a common denominator. 6 and 4 both divide into 12.12
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.5/6 = 10/12 and 1/4 = 3/12
- Subtract the top numbers. The bottom number stays the same.10 - 3 = 7, so 7/12
- Write the answer. The fraction cannot be simplified.7/12
- Write the answer. 7/12
Check. 10/12 - 3/12 = 7/12. ✓
Watch out. Do not subtract the bottoms: 5/6 - 1/4 is not 4/2.
Exercise 3D Practice: adding and subtracting fractions
Non-calculatorMethod. The bottoms are the same, so add the tops.
- The bottom numbers are the same. So add the top numbers and keep the bottom number.2 + 4 = 6, so 6/9
- Simplify the answer. Divide the top and bottom by 3.6/9 = 2/3
- Write the answer. 2/3
Check. The total is less than one whole, so it is less than 1. ✓
Method. The bottoms are the same, so add the tops.
- Find a common denominator. 10 and 2 both divide into 10.10
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.3/10 = 3/10 and 1/2 = 5/10
- Add the top numbers. The bottom number stays the same.3 + 5 = 8, so 8/10
- Simplify the answer. Divide the top and bottom by 2.8/10 = 4/5
- Write the answer. 4/5
Check. The total is less than one whole, so it is less than 1. ✓
Method. The bottoms are the same, so add the tops.
- The bottom numbers are the same. So add the top numbers and keep the bottom number.4 + 2 = 6, so 6/7
- Write the answer. The fraction cannot be simplified.6/7
- Write the answer. 6/7
Check. The total is less than one whole, so it is less than 1. ✓
Method. Find a common denominator, make equivalent fractions, then add.
- Find a common denominator. 2 and 3 both divide into 6.6
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.1/2 = 3/6 and 1/3 = 2/6
- Add the top numbers. The bottom number stays the same.3 + 2 = 5, so 5/6
- Write the answer. The fraction cannot be simplified.5/6
- Write the answer. 5/6
Check. 5/6 is the sum in its simplest form. ✓
Method. Find a common denominator, make equivalent fractions, then add.
- Find a common denominator. 4 and 8 both divide into 8.8
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.3/4 = 6/8 and 1/8 = 1/8
- Add the top numbers. The bottom number stays the same.6 + 1 = 7, so 7/8
- Write the answer. The fraction cannot be simplified.7/8
- Write the answer. 7/8
Check. 7/8 is the sum in its simplest form. ✓
Method. Find a common denominator, make equivalent fractions, then add.
- Find a common denominator. 5 and 10 both divide into 10.10
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.2/5 = 4/10 and 1/10 = 1/10
- Add the top numbers. The bottom number stays the same.4 + 1 = 5, so 5/10
- Simplify the answer. Divide the top and bottom by 5.5/10 = 1/2
- Write the answer. 1/2
Check. 1/2 is the sum in its simplest form. ✓
Method. Find a common denominator, make equivalent fractions, then subtract.
- Find a common denominator. 6 and 3 both divide into 6.6
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.5/6 = 5/6 and 1/3 = 2/6
- Subtract the top numbers. The bottom number stays the same.5 - 2 = 3, so 3/6
- Simplify the answer. Divide the top and bottom by 3.3/6 = 1/2
- Write the answer. 1/2
Check. 1/2 + 1/3 = 5/6. ✓
Method. Find a common denominator, make equivalent fractions, then subtract.
- Find a common denominator. 8 and 4 both divide into 8.8
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.7/8 = 7/8 and 1/4 = 2/8
- Subtract the top numbers. The bottom number stays the same.7 - 2 = 5, so 5/8
- Write the answer. The fraction cannot be simplified.5/8
- Write the answer. 5/8
Check. 5/8 + 1/4 = 7/8. ✓
Method. Find a common denominator, make equivalent fractions, then subtract.
- Find a common denominator. 3 and 9 both divide into 9.9
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.2/3 = 6/9 and 2/9 = 2/9
- Subtract the top numbers. The bottom number stays the same.6 - 2 = 4, so 4/9
- Write the answer. The fraction cannot be simplified.4/9
- Write the answer. 4/9
Check. 4/9 + 2/9 = 2/3. ✓
Method. Change each mixed number to an improper fraction, then add.
- Change to improper fractions. 2 1/3 = 7/3 and 1 1/2 = 3/2.7/3 and 3/2
- Make the bottoms the same. A common denominator of 3 and 2 is 6: 7/3 = 14/6 and 3/2 = 9/6.14/6 and 9/6
- Add the tops. 14 + 9 = 23, so 23/6.23/6
- Change back to a mixed number. 23 ÷ 6 = 3 remainder 5.3 5/6
- Write the answer. 3 5/6
Check. 3 5/6 = 23/6. ✓
Method. Both mixed numbers have the same bottom, so subtract the whole numbers and the fractions.
- Subtract the whole numbers. 3 - 1 = 2.2
- Subtract the fractions. 3/4 - 1/4 = 2/4, which is 1/2.2/4 = 1/2
- Put them together. 2 + 1/2 = 2 1/2.2 1/2
- Write the answer. 2 1/2
Check. 2 1/2 + 1 1/4 = 3 3/4. ✓
Method. Add the two fractions with a common denominator.
- Find a common denominator. 5 and 4 both divide into 20.20
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.3/5 = 12/20 and 1/4 = 5/20
- Add the top numbers. The bottom number stays the same.12 + 5 = 17, so 17/20
- Write the answer. The fraction cannot be simplified.17/20
- Write the answer. 17/20
Check. 17/20 is about 0.85 km. ✓
Method. Find a common denominator before you add.
- Make equivalent fractions. 1/2 = 3/6 and 1/3 = 2/6.3/6 and 2/6
- Add the tops. 3 + 2 = 5, so 5/6.5/6
- Write the answer. No, the correct answer is 5/6, because 1/2 is 3/6 and 1/3 is 2/6.
Check. 5/6 is 0.83, not 2/5 which is 0.4. ✓
Method. Find a common denominator of 10 and 5, which is 10.
- Find a common denominator. 10 and 5 both divide into 10.10
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.9/10 = 9/10 and 3/5 = 6/10
- Subtract the top numbers. The bottom number stays the same.9 - 6 = 3, so 3/10
- Write the answer. The fraction cannot be simplified.3/10
- Write the answer. 3/10
Check. 3/5 = 6/10, so 9/10 - 6/10 = 3/10. ✓
Multiplying and dividing fractions, and decimals
Rule
To multiply a fraction by a whole number, multiply the top and keep the bottom. Then simplify.
To multiply two fractions, multiply the tops and multiply the bottoms, then simplify.
To divide a fraction by a whole number, keep the top and multiply the bottom by the whole number.
A fraction is a division: 4/5 means 4 ÷ 5 = 0.8.
Key ideas
- Fraction × whole number: multiply the top.
- Fraction × fraction: multiply the tops and the bottoms.
- Fraction ÷ whole number: multiply the bottom.
- A fraction can be written as a decimal by making the bottom 10, 100 or 1000.
Method. Multiply the top by 8, then simplify.
- Multiply the top number by the whole number. 3 × 8 = 24, so the top becomes 24.3 × 8 = 24
- Simplify the fraction. Divide the top and the bottom by 4.24/4 = 6
- Write the answer. 6
Check. 8 ÷ 4 = 2 and 2 × 3 = 6. ✓
Watch out. Simplify 24/4 to get a whole number: 6.
Method. Multiply the tops, multiply the bottoms, then simplify.
- Multiply the top numbers. 2 × 3 = 6.2 × 3 = 6
- Multiply the bottom numbers. 3 × 5 = 15.3 × 5 = 15
- Simplify. Divide the top and bottom by 3.6/15 = 2/5
- Write the answer. 2/5
Check. 6/15 = 2/5 when both are divided by 3. ✓
Method. Keep the top, and multiply the bottom by 6.
- Keep the top number the same. The top stays at 3.3
- Multiply the bottom number by the whole number. Sharing into 6 equal parts makes each part 6 times smaller.4 × 6 = 24
- Simplify. Divide the top and bottom by 3.3/24 = 1/8
- Write the answer. 1/8
Check. 1/8 × 6 = 6/8 = 3/4. ✓
Exercise 3E Practice: multiplying and dividing fractions
Non-calculatorMethod. Multiply the top by the whole number, then simplify.
- Multiply the top number by the whole number. 3 × 4 = 12, so the top becomes 12.3 × 4 = 12
- Simplify the fraction. Divide the top and the bottom by 4.12/8 = 1 1/2
- Write the answer. 1 1/2
Check. 1 1/2 = 3/8 × 4. ✓
Method. Multiply the top by the whole number, then simplify.
- Multiply the top number by the whole number. 5 × 9 = 45, so the top becomes 45.5 × 9 = 45
- Simplify the fraction. Divide the top and the bottom by 3.45/6 = 7 1/2
- Write the answer. 7 1/2
Check. 7 1/2 = 5/6 × 9. ✓
Method. Multiply the top by the whole number, then simplify.
- Multiply the top number by the whole number. 2 × 15 = 30, so the top becomes 30.2 × 15 = 30
- Simplify the fraction. Divide the top and the bottom by 5.30/5 = 6
- Write the answer. 6
Check. 6 = 2/5 × 15. ✓
Method. Multiply the top by the whole number, then simplify.
- Multiply the top number by the whole number. 5 × 8 = 40, so the top becomes 40.5 × 8 = 40
- Simplify the fraction. Divide the top and the bottom by 4.40/12 = 3 1/3
- Write the answer. 3 1/3
Check. 3 1/3 = 5/12 × 8. ✓
Method. Multiply the tops and the bottoms, then simplify.
- Multiply the top numbers. 2 × 3 = 6.2 × 3 = 6
- Multiply the bottom numbers. 3 × 5 = 15.3 × 5 = 15
- Simplify. Divide the top and bottom by 3.6/15 = 2/5
- Write the answer. 2/5
Check. 2/5 is the answer in its simplest form. ✓
Method. Multiply the tops and the bottoms, then simplify.
- Multiply the top numbers. 3 × 2 = 6.3 × 2 = 6
- Multiply the bottom numbers. 4 × 9 = 36.4 × 9 = 36
- Simplify. Divide the top and bottom by 6.6/36 = 1/6
- Write the answer. 1/6
Check. 1/6 is the answer in its simplest form. ✓
Method. Multiply the tops and the bottoms, then simplify.
- Multiply the top numbers. 5 × 3 = 15.5 × 3 = 15
- Multiply the bottom numbers. 6 × 10 = 60.6 × 10 = 60
- Simplify. Divide the top and bottom by 15.15/60 = 1/4
- Write the answer. 1/4
Check. 1/4 is the answer in its simplest form. ✓
Method. Keep the top and multiply the bottom by the whole number.
- Keep the top number the same. The top stays at 3.3
- Multiply the bottom number by the whole number. Sharing into 6 equal parts makes each part 6 times smaller.4 × 6 = 24
- Simplify. Divide the top and bottom by 3.3/24 = 1/8
- Write the answer. 1/8
Check. 1/8 × 6 = 3/4. ✓
Method. Keep the top and multiply the bottom by the whole number.
- Keep the top number the same. The top stays at 2.2
- Multiply the bottom number by the whole number. Sharing into 4 equal parts makes each part 4 times smaller.5 × 4 = 20
- Simplify. Divide the top and bottom by 2.2/20 = 1/10
- Write the answer. 1/10
Check. 1/10 × 4 = 2/5. ✓
Method. Keep the top and multiply the bottom by the whole number.
- Keep the top number the same. The top stays at 5.5
- Multiply the bottom number by the whole number. Sharing into 10 equal parts makes each part 10 times smaller.6 × 10 = 60
- Simplify. Divide the top and bottom by 5.5/60 = 1/12
- Write the answer. 1/12
Check. 1/12 × 10 = 5/6. ✓
Method. Make the bottom 10 by multiplying the top and bottom by 2.
- Make the bottom number a power of 10. 5 goes into 10 exactly, so multiply the top and bottom by 2.4/5 = 8/10
- Read the fraction as a decimal. 8 hundredths or thousandths is written with 1 decimal place.8/10 = 0.8
- Write the answer. 0.8
Check. 0.8 × 5 = 4. ✓
Method. Make the bottom 100 by multiplying by 25.
- Make the bottom number a power of 10. 4 goes into 100 exactly, so multiply the top and bottom by 25.3/4 = 75/100
- Read the fraction as a decimal. 75 hundredths or thousandths is written with 2 decimal places.75/100 = 0.75
- Write the answer. 0.75
Check. 0.75 × 4 = 3. ✓
Method. Make the bottom 1000 by multiplying by 125.
- Make the bottom number a power of 10. 8 goes into 1000 exactly, so multiply the top and bottom by 125.1/8 = 125/1000
- Read the fraction as a decimal. 125 hundredths or thousandths is written with 3 decimal places.125/1000 = 0.125
- Write the answer. 0.125
Check. 0.125 × 8 = 1. ✓
Method. Multiply 3/4 by 8.
- Multiply the top number by the whole number. 3 × 8 = 24, so the top becomes 24.3 × 8 = 24
- Simplify the fraction. Divide the top and the bottom by 4.24/4 = 6
- Write the answer. 6
Check. 8 jugs of 0.75 litres is 6 litres. ✓
Method. Divide 3/4 by 6.
- Keep the top number the same. The top stays at 3.3
- Multiply the bottom number by the whole number. Sharing into 6 equal parts makes each part 6 times smaller.4 × 6 = 24
- Simplify. Divide the top and bottom by 3.3/24 = 1/8
- Write the answer. 1/8
Check. 6 × 1/8 = 6/8 = 3/4. ✓
Method. Multiply, then simplify by 5 or by 2.
- Multiply the top numbers. 4 × 5 = 20.4 × 5 = 20
- Multiply the bottom numbers. 5 × 6 = 30.5 × 6 = 30
- Simplify. Divide the top and bottom by 10.20/30 = 2/3
- Write the answer. 2/3
Check. 20/30 = 2/3. ✓
Method. Divide the top and multiply the bottom by 2.
- Divide the top and multiply the bottom. 1/2 ÷ 2 = 1/(2 × 2).1/4
- Compare. 1/4 is smaller than 1/2.1/4 < 1/2
- Write the answer. Because you are sharing half a whole into 2 equal parts, so each part is smaller than half: the answer is 1/4.
Check. 1/4 × 2 = 1/2. ✓
Chapter summary
| Skill | Method |
|---|---|
| Simplify | Divide the top and bottom by their highest common factor: 36/48 = 3/4. |
| Equivalent fraction | Multiply the top and bottom by the same number: 3/5 = 12/20. |
| Compare | Write with a common denominator, then compare the tops. |
| Mixed and improper | 2 3/4 = 11/4 (2 × 4 + 3); 17/5 = 3 2/5 (17 ÷ 5 = 3 remainder 2). |
| Add and subtract | Common denominator, equivalent fractions, then add or subtract the tops. |
| Multiply | Fraction × whole: multiply the top. Fraction × fraction: multiply tops and bottoms. |
| Divide by whole | Keep the top, multiply the bottom: 3/4 ÷ 6 = 3/24 = 1/8. |
| Decimal | Make the bottom 10, 100 or 1000: 4/5 = 8/10 = 0.8. |
Can you…?
- I can simplify a fraction to its simplest form
- I can find equivalent fractions and compare fractions with different bottoms
- I can change between mixed numbers and improper fractions
- I can add and subtract fractions with different bottoms
- I can multiply and divide fractions, and simplify the answer
- I can write a fraction as a decimal
Key terms
- equivalent fraction
- a fraction with the same value written with different numbers
- simplest form
- a fraction that cannot be made smaller by dividing the top and bottom by the same number
- highest common factor
- the biggest number that divides exactly into two or more numbers
- common denominator
- the same bottom number for two or more fractions
- mixed number
- a whole number with a fraction, such as 2 3/4
- improper fraction
- a fraction with a top number bigger than the bottom, such as 11/4
- proper fraction
- a fraction with a top number smaller than the bottom, such as 3/4
Exercise 3Z Check-up
Non-calculatorMethod. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 42 and 56 is 14.HCF of 42 and 56 is 14
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.42 ÷ 14 = 3, 56 ÷ 14 = 4
- Write the answer. 3/4
Check. 3/4 × 14 = 42/56 when both are simplified. ✓
Method. Multiply the top and bottom by 3.
- Multiply the top and the bottom by the same number. Both are multiplied by 3, so the value of the fraction does not change.5 × 3 = 15 and 8 × 3 = 24
- Write the answer. 5/8
Check. 15/24 = 5/8. ✓
Method. Use the common denominator 24.
- Find a common denominator. 6 and 8 both divide into 24.24
- Write both fractions with that denominator. Multiply each top and bottom by the same number.5/6 = 20/24 and 7/8 = 21/24
- Compare the top numbers. 20 and 21 tell us which fraction is bigger.20 < 21, so 5/6 < 7/8
- Write the answer. <
Check. 5/6 = 20/24 and 7/8 = 21/24. ✓
Method. Divide 19 by 6.
- Divide the top number by the bottom number. 19 ÷ 6 = 3 with 1 left over.19 ÷ 6 = 3 r 1
- Write the answer as a mixed number. The whole number is 3, and the 1 left over goes over 6.3 1/6
- Write the answer. 3 1/6
Check. 3 × 6 + 1 = 19. ✓
Method. Multiply the whole number by the bottom and add the top.
- Multiply the whole number by the bottom number. Each whole has 9 parts, so 3 wholes have 3 × 9 parts.3 × 9 = 27
- Add the top number. Add the 5 parts that are left over.27 + 5 = 32
- Keep the same bottom number. The size of each part does not change.32/9
- Write the answer. 32/9
Check. 32/9 = 3 5/9. ✓
Method. The bottoms are the same, so add the tops.
- The bottom numbers are the same. So add the top numbers and keep the bottom number.3 + 2 = 5, so 5/7
- Write the answer. The fraction cannot be simplified.5/7
- Write the answer. 5/7
Check. 5/7 - 2/7 = 3/7. ✓
Method. Make the bottoms the same, then subtract.
- Find a common denominator. 9 and 3 both divide into 9.9
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.7/9 = 7/9 and 1/3 = 3/9
- Subtract the top numbers. The bottom number stays the same.7 - 3 = 4, so 4/9
- Write the answer. The fraction cannot be simplified.4/9
- Write the answer. 4/9
Check. 4/9 + 3/9 = 7/9. ✓
Method. Multiply the top by 15, then simplify.
- Multiply the top number by the whole number. 2 × 15 = 30, so the top becomes 30.2 × 15 = 30
- Simplify the fraction. Divide the top and the bottom by 5.30/5 = 6
- Write the answer. 6
Check. 6 × 5 = 30 and 2 × 15 = 30, so the answer is 6. ✓
Method. Multiply the tops and the bottoms, then simplify.
- Multiply the top numbers. 5 × 3 = 15.5 × 3 = 15
- Multiply the bottom numbers. 6 × 10 = 60.6 × 10 = 60
- Simplify. Divide the top and bottom by 15.15/60 = 1/4
- Write the answer. 1/4
Check. 15/60 = 1/4. ✓
Method. Make the bottom 10 by multiplying by 2.
- Make the bottom number a power of 10. 5 goes into 10 exactly, so multiply the top and bottom by 2.3/5 = 6/10
- Read the fraction as a decimal. 6 hundredths or thousandths is written with 1 decimal place.6/10 = 0.6
- Write the answer. 0.6
Check. 0.6 × 5 = 3. ✓
Total 19 marks. Allow about 19 minutes.
Exercise 3X Practice test questions
Non-calculatorMethod. Divide the top and bottom by the highest common factor.
- Find a number that divides into both the top and the bottom. The highest common factor of 48 and 64 is 16.HCF of 48 and 64 is 16
- Divide the top and the bottom by it. Dividing both by the same number keeps the fraction the same size.48 ÷ 16 = 3, 64 ÷ 16 = 4
- Write the answer. 3/4
Check. 3/4 is the simplest form. ✓
Method. Multiply the top and bottom by 4.
- Multiply the top and the bottom by the same number. Both are multiplied by 4, so the value of the fraction does not change.2 × 4 = 8 and 3 × 4 = 12
- Write the answer. 2/3
Check. 8/12 = 2/3. ✓
Method. Use the common denominator 35.
- Find a common denominator. 5 and 7 both divide into 35.35
- Write both fractions with that denominator. Multiply each top and bottom by the same number.3/5 = 21/35 and 4/7 = 20/35
- Compare the top numbers. 21 and 20 tell us which fraction is bigger.21 > 20, so 3/5 > 4/7
- Write the answer. >
Check. 21/35 and 20/35. ✓
Method. Add the tops.
- The bottom numbers are the same. So add the top numbers and keep the bottom number.5 + 2 = 7, so 7/9
- Write the answer. The fraction cannot be simplified.7/9
- Write the answer. 7/9
Check. 7/9 - 2/9 = 5/9. ✓
Method. Find the common denominator 12, make equivalent fractions, then add.
- Find a common denominator. 4 and 6 both divide into 12.12
- Make equivalent fractions. Multiply each top and bottom to get the common denominator.3/4 = 9/12 and 1/6 = 2/12
- Add the top numbers. The bottom number stays the same.9 + 2 = 11, so 11/12
- Write the answer. The fraction cannot be simplified.11/12
- Write the answer. 11/12
Check. 9/12 + 2/12 = 11/12. ✓
Method. Change to improper fractions with the same bottom, then subtract.
- Improper fractions. 4 1/2 = 18/4 and 2 3/4 = 11/4.18/4 and 11/4
- Subtract. 18 - 11 = 7, so 7/4.7/4
- Change back. 7 ÷ 4 = 1 remainder 3.1 3/4
- Write the answer. 1 3/4
Check. 1 3/4 + 2 3/4 = 4 1/2. ✓
Method. Multiply the top by 16, then simplify.
- Multiply the top number by the whole number. 5 × 16 = 80, so the top becomes 80.5 × 16 = 80
- Simplify the fraction. Divide the top and the bottom by 8.80/8 = 10
- Write the answer. 10
Check. 10 × 8 = 80 and 80/8 = 10. ✓
Method. Multiply the tops and bottoms, then simplify.
- Multiply the top numbers. 3 × 4 = 12.3 × 4 = 12
- Multiply the bottom numbers. 5 × 9 = 45.5 × 9 = 45
- Simplify. Divide the top and bottom by 3.12/45 = 4/15
- Write the answer. 4/15
Check. 12/45 = 4/15. ✓
Method. Keep the top and multiply the bottom by 2.
- Keep the top number the same. The top stays at 4.4
- Multiply the bottom number by the whole number. Sharing into 2 equal parts makes each part 2 times smaller.9 × 2 = 18
- Simplify. Divide the top and bottom by 2.4/18 = 2/9
- Write the answer. 2/9
Check. 2/9 × 2 = 4/9. ✓
Method. Make the bottom 100 by multiplying by 5.
- Make the bottom number a power of 10. 20 goes into 100 exactly, so multiply the top and bottom by 5.7/20 = 35/100
- Read the fraction as a decimal. 35 hundredths or thousandths is written with 2 decimal places.35/100 = 0.35
- Write the answer. 0.35
Check. 0.35 × 20 = 7. ✓
Method. Multiply the top by 3, then simplify.
- Multiply the top. 2 × 3 = 6, so 6/3.6/3
- Simplify. Divide 6 by 3 to get a whole number.2
- Write the answer. 2 cups, because 2/3 × 3 = 6/3 = 2.
Check. 2/3 of a cup for each batch: 3 batches make 2 cups. ✓