Subtraction within 20
The question
15 − 6
15−6
15−5=10
6=5+1
10−1=9
- 15 − 6. The ones cannot cover it — 5 is less than 6 — so drop to the ten below first.
- 15 − 5 = 10. That used 5 of the 6, leaving 1 still to take.
- Then the rest off the ten: 10 − 1 = 9.
How it works.
- 01
15 − 6. The ones cannot cover it — 5 is less than 6 — so drop to the ten below first.
- 02
15 − 5 = 10. That used 5 of the 6, leaving 1 still to take.
- 03
Then the rest off the ten: 10 − 1 = 9.