← Methods
Make Ten
Nobody really adds seven and eight. They fill the seven up to ten and add what is left over — the same sum, in two easy steps instead of one hard one.
When it works
Adding a single digit to a number that does not end in zero.
Worked through
47 + 8 = 55
- 47 + 3 = 50Top it up to the next ten — that takes 3.
- 50 + 5 = 55Then add the 5 that is left.
10 problems, every one of them this method.