Subtraction (up to 20)
Taking Away and Counting Back
Subtraction means taking some away to find how many are left. We use the sign − (minus).
One easy way is to count back. To find 8 − 3, start at 8 and count back three: 7, 6, 5. So 8 − 3 = 5.
Example 1: Subtract: 9 − 2
Count back from 9: 8, 7. So 9 − 2 = 7.
Example 2: Subtract: 10 − 4
Count back from 10: 9, 8, 7, 6. So 10 − 4 = 6.
Quick recap
- Subtraction (−) takes away to find what is left.
- Count back to subtract quickly.
- The bigger number comes first in 'take away'.
✓ Quick check
What is 7 − 3?
7 − 3 = 4.
Count back from 12: 12 − 2 = ?
12 → 11, 10. So 12 − 2 = 10.
Subtraction Facts: Take Away Zero and All
If you take away zero, nothing changes: 6 − 0 = 6.
If you take away all of a number from itself, you get 0: 7 − 7 = 0. Subtraction is the opposite of addition: since 4 + 3 = 7, we know 7 − 3 = 4.
Example 1: Subtract: 8 − 0
Taking away zero changes nothing, so 8 − 0 = 8.
Example 2: Subtract: 5 − 5
Taking away all of it leaves nothing, so 5 − 5 = 0.
Quick recap
- Take away 0 → the number stays the same.
- Take away the whole number → you get 0.
- Addition and subtraction are opposites.
✓ Quick check
10 − 0 = ?
Taking away zero keeps it the same: 10 − 0 = 10.
9 − 9 = ?
Taking away all of it leaves 0.
Subtraction Word Problems
We subtract to find how many are left or how many more. Words like left, remain, fewer and how many more tell us to subtract.
Example 1: Meera had 10 sweets. She ate 4. How many are left?
10 − 4 = 6 sweets left.
Example 2: There are 8 birds. 3 fly away. How many remain?
8 − 3 = 5 birds.
Quick recap
- 'Left', 'remain', 'fewer' mean subtract.
- Start with the total and take away.
✓ Quick check
Aarav had 9 toffees and gave away 5. How many are left?
9 − 5 = 4 toffees.
A jar had 15 biscuits. 6 were eaten. How many remain?
15 − 6 = 9 biscuits.
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