Addition and subtraction within 100, step by step
Once two-digit addition and two-digit subtraction have each been practiced alone, the next step is meeting them together.
The question
87 − 19
19=10+9
87−10=77
77−9=68
- 87 − 19, across the line. Split only the 19 — the amount being taken away — and take it off in two goes.
- The tens first: 87 − 10 = 77.
- Then the ones off what is left: 77 − 9 = 68. Nothing had to borrow, because each go came off the whole number rather than off one place.
How it works.
- 01
87 − 19, across the line. Split only the 19 — the amount being taken away — and take it off in two goes.
- 02
The tens first: 87 − 10 = 77.
- 03
Then the ones off what is left: 77 − 9 = 68. Nothing had to borrow, because each go came off the whole number rather than off one place.