Year 1: Double and half
Part of the Year 1 length and height chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Double and half
Double means two times as much. A rope that is double another rope is two times as long. To double a number of cubes, make two equal lots of it.
Half means share into two equal parts. When you halve a strip, each half is the same length. Halving is the opposite of doubling.
Key ideas
- Double means two equal lots of the same amount.
- Half means share into two equal parts.
- Double 4 is 8, because 4 + 4 = 8.
- Half of 8 is 4, because 4 + 4 = 8.
Method. Double means two equal lots of the same number.
- Start with 4. This is the length we want to double.4
- Add 4 again. Two equal lots make double.4 + 4 = 8
- Write the answer. 8 cubes
Check. Half of 8 is 4, so double 4 must be 8. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Half means share it into two equal parts.
- Start with 10. This is the whole strip.10
- Share it into two equal parts. Each part must be exactly the same length.10 ÷ 2 = 5
- Write the answer. 5 cubes
Check. Put the two halves back together: 5 + 5 = 10. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Double means two equal lots of the same number.
- Start with 3. This is the length we want to double.3
- Add 3 again. Two equal lots make double.3 + 3 = 6
- Write the answer. 6 paper clips
Check. Half of 6 is 3, so double 3 must be 6. ✓
Watch out. Double means add the same number again. It is not add one more.
Watch out
Watch out: double means add the same amount again. It does not mean add one more. Double 3 is 6, not 4.
Exam tip
Grown-up tip. Use two rows of buttons or cubes. Make one row, then build an identical row next to it. Ask: “How many altogether? Is it double?” For halves, share a row of buttons one at a time, so each person gets the same.
Exercise 7E Double and half
Non-calculatorMethod. Double means two equal lots of the same number.
- Start with 2. This is the length we want to double.2
- Add 2 again. Two equal lots make double.2 + 2 = 4
- Write the answer. 4 cubes
Check. Half of 4 is 2, so double 2 must be 4. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Double means two equal lots of the same number.
- Start with 4. This is the length we want to double.4
- Add 4 again. Two equal lots make double.4 + 4 = 8
- Write the answer. 8 cubes
Check. Half of 8 is 4, so double 4 must be 8. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Double means two equal lots of the same number.
- Start with 5. This is the length we want to double.5
- Add 5 again. Two equal lots make double.5 + 5 = 10
- Write the answer. 10
Check. Half of 10 is 5, so double 5 must be 10. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Half means share it into two equal parts.
- Start with 6. This is the whole strip.6
- Share it into two equal parts. Each part must be exactly the same length.6 ÷ 2 = 3
- Write the answer. 3 cubes
Check. Put the two halves back together: 3 + 3 = 6. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Half means share it into two equal parts.
- Start with 8. This is the whole strip.8
- Share it into two equal parts. Each part must be exactly the same length.8 ÷ 2 = 4
- Write the answer. 4 cubes
Check. Put the two halves back together: 4 + 4 = 8. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Half means share it into two equal parts.
- Start with 8. This is the whole strip.8
- Share it into two equal parts. Each part must be exactly the same length.8 ÷ 2 = 4
- Write the answer. 4
Check. Put the two halves back together: 4 + 4 = 8. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Double B is the same as two lots of A.
- Look at strip A. Strip A has 3 cubes.A = 3
- Find double 3. Double 3 means 3 + 3.3 + 3 = 6
- Compare with strip B. Strip B has 6 cubes, which matches double 3.B = 6
- Write the answer. Yes. B is double A.
Check. Halve 6 to check: 6 ÷ 2 = 3. That is A. ✓
Watch out. Double means two lots of the same number.
Method. Find double 4, then compare it with strip D.
- Look at strip C. Strip C has 4 cubes.C = 4
- Find double 4. Double 4 means 4 + 4.4 + 4 = 8
- Compare with strip D. Strip D has 9 cubes. That is not 8.D = 9, and 9 is not 8
- Write the answer. No. Double 4 is 8, not 9.
Check. Double 4 is 8, and strip D has 9, so the two strips are not double. ✓
Watch out. Count the cubes in both strips before you decide.
Method. Double means two equal lots of the same number.
- Start with 5. This is the length we want to double.5
- Add 5 again. Two equal lots make double.5 + 5 = 10
- Write the answer. 10 cubes
Check. Half of 10 is 5, so double 5 must be 10. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Double means two equal lots of the same number.
- Start with 1. This is the length we want to double.1
- Add 1 again. Two equal lots make double.1 + 1 = 2
- Write the answer. 2
Check. Half of 2 is 1, so double 1 must be 2. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Double means two equal lots of the same number.
- Start with 2. This is the length we want to double.2
- Add 2 again. Two equal lots make double.2 + 2 = 4
- Write the answer. 4
Check. Half of 4 is 2, so double 2 must be 4. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Double means two equal lots of the same number.
- Start with 4. This is the length we want to double.4
- Add 4 again. Two equal lots make double.4 + 4 = 8
- Write the answer. 8
Check. Half of 8 is 4, so double 4 must be 8. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Double means two equal lots of the same number.
- Start with 5. This is the length we want to double.5
- Add 5 again. Two equal lots make double.5 + 5 = 10
- Write the answer. 10
Check. Half of 10 is 5, so double 5 must be 10. ✓
Watch out. Double means add the same number again. It is not add one more.
Method. Half means share it into two equal parts.
- Start with 4. This is the whole strip.4
- Share it into two equal parts. Each part must be exactly the same length.4 ÷ 2 = 2
- Write the answer. 2
Check. Put the two halves back together: 2 + 2 = 4. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Half means share it into two equal parts.
- Start with 2. This is the whole strip.2
- Share it into two equal parts. Each part must be exactly the same length.2 ÷ 2 = 1
- Write the answer. 1
Check. Put the two halves back together: 1 + 1 = 2. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Half means share it into two equal parts.
- Start with 10. This is the whole strip.10
- Share it into two equal parts. Each part must be exactly the same length.10 ÷ 2 = 5
- Write the answer. 5
Check. Put the two halves back together: 5 + 5 = 10. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Half means share it into two equal parts.
- Start with 6. This is the whole strip.6
- Share it into two equal parts. Each part must be exactly the same length.6 ÷ 2 = 3
- Write the answer. 3
Check. Put the two halves back together: 3 + 3 = 6. ✓
Watch out. The two parts must be equal. Count each part to check.
Method. Try doubling and then halving, one step at a time.
- Start with 3. This is the length of the rope.3
- Double it. Double 3 is 3 + 3.3 + 3 = 6
- Halve it again. Half of 6 is 3.6 ÷ 2 = 3
- Write the answer. Tom is right, because he gets back to 3.Yes. Double 3 is 6, and half of 6 is 3.
Check. Doubling and halving undo each other. ✓
Watch out. Halving undoes doubling, so you get back to where you started.