Year 1 Handbook
Subtraction within 20
Understand subtraction as taking away and as finding a difference.
What you are learning
Understand subtraction as taking away and as finding a difference.
Key idea
Subtraction can show what is left after taking away, or the gap between two numbers.
8910111213count back 5
Worked example
13 - 5
13 - 5 = 8
- Start with 13 because it is the whole amount.
- Take away 5 by counting back: 12, 11, 10, 9, 8.
- The number left is 8.
Therefore, 13 - 5 = 8.
Another way
Count up to find the difference
For 13 - 8, count up from 8 to 13: 9, 10, 11, 12, 13. That is 5 steps, so the difference is 5.
Why this works
Subtraction undoes addition. If 13 - 5 = 8, then 8 + 5 = 13.
Common mistake
Remember
Use the related addition fact to check a subtraction.
Vocabulary
- subtract
- Take away or find the difference.
- difference
- The gap between two numbers.
- whole
- The amount we start with before taking away.
- left
- The amount remaining after subtraction.
Try one
Have a go before revealing the answer. These are optional learning checks: they are not scored and do not change your practice record.
Complete: 15 - 6 = ?
Which addition fact checks 12 - 4 = 8?