5.3.2

Addition & Subtraction

Test yourself

Addition in your Head

You can use knowledge of place value and number bonds to help us add.

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67 + 91

  • When trying to work out 67 + 91, you need to use your number bonds.
    • You know that 7 + 1 = 8.
    • So your 'ones' must be 8.
Illustrative background for 'Tens'Illustrative background for 'Tens' ?? "content

'Tens'

  • You know that 9 + 6 = 15.
    • So your 'tens' must be 15.
    • 15 'tens' is the same as 5 'tens' and 1 'hundred'.
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And the answer is...

  • So there are:
    • 8 'ones'.
    • 5 'tens'.
    • 1 'hundred'.
  • The answer is to 67 + 91 is 158.
Illustrative background for 98 + 15Illustrative background for 98 + 15 ?? "content

98 + 15

  • This is the same even if there is carrying to do!
    • You know that 8 + 5 = 13.
    • So your 'ones' must be 13.
    • You will need to carry the 1 into the 'tens' column.
Illustrative background for The 'tens'Illustrative background for The 'tens' ?? "content

The 'tens'

  • You know that 9 + 1 = 10.
  • You need to add 1 more from the 1 you carried from the 'ones'.
    • So your 'tens' must be 11.
    • 11 'tens' is the same as 1 'ten' and 1 'hundred'.
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And the answer is...

  • So there are:
    • 3 'ones'.
    • 1 'ten'.
    • 1 'hundred'.
  • The answer is to 98 + 15 is 113.

Subtraction in your Head

You can use knowledge of place value and number bonds to help us subtract.

Illustrative background for 67 − 23Illustrative background for 67 − 23 ?? "content

67 − 23

  • When trying to work out 67 − 23, you need to use your number bonds.
    • You know that 7 − 3 = 4.
    • So your 'ones' must be 4.
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'Tens'

  • You know that 6 − 2 = 4.
    • So your 'tens' must be 4.
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And the answer is...

  • So there are:
    • 4 'ones'.
    • 4 'tens'.
  • The answer is to 67 − 23 is 44.
Illustrative background for 73 − 18Illustrative background for 73 − 18 ?? "content

73 − 18

  • This is the same even if there is borrowing (exchanging) to do!
  • You can use number bonds to help you when you need to borrow (exchange) in a subtraction.
    • You know that 3 + 5 + 10 = 18.
    • So 73 − 3 − 5 − 10 = 73 − 18.
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And the answer is...

  • 73 − 3 − 5 − 10 = 55.

Jump to other topics

1Year 5 - Number

2Year 5 - Measurement

3Year 5 - Geometry

4Year 5 - Statistics

5Year 6 - Number

6Year 6 - Ratio & Proportion

7Year 6 - Algebra

8Year 6 - Measurement

9Year 6 - Statistics

9.1Displaying Data

9.2Averages

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