Addition & Subtraction
Maths: Year 5 & 6 National Curriculum, topic 5.3.2
Addition in your Head
You can use knowledge of place value and number bonds to help us add.
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.
'Tens'
- You know that 9 + 6 = 15.
- So your 'tens' must be 15.
- 15 'tens' is the same as 5 'tens' and 1 'hundred'.
And the answer is...
- So there are:
- 8 'ones'.
- 5 'tens'.
- 1 'hundred'.
- The answer is to 67 + 91 is 158.
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.
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'.
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.
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.
'Tens'
- You know that 6 − 2 = 4.
- So your 'tens' must be 4.
And the answer is...
- So there are:
- 4 'ones'.
- 4 'tens'.
- The answer is to 67 − 23 is 44.
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.
And the answer is...
- 73 − 3 − 5 − 10 = 55.
Test yourself on Addition & Subtraction
What is 56 + 83?
What is 21 + 93?
What is 48 + 37?
What is 75 − 33?
What is 86 − 59?