Explain Addition and Subtraction Strategies — Explain the Strategy

Explain why the strategy gives the right answer.

ExampleMaya works out 88 − 65 like this:
80 − 60 = 20, and 8 − 5 = 3, then 20 + 3 = 23.
Why does breaking the numbers into tens and ones work here? Because 88 is 80 + 8 and 65 is 60 + 5. You can take the tens from the tens and the ones from the ones, then put what is left together: 20 + 3 = 23. (This works because each top digit is big enough to subtract from — no borrowing.)

1.Maya works out 76 − 33 like this:
70 − 30 = 40, and 6 − 3 = 3, then 40 + 3 = 43.
Why does breaking the numbers into tens and ones work here?
2.Ben works out 50 − 16 like this:
16 is close to 20, so 50 − 20 = 30, then add 4 back: 34.
Why does subtracting too much and then adding it back work?
3.Leo works out 36 + 27 like this:
30 + 20 = 50, and 6 + 7 = 13, then 50 + 13 = 63.
Why does breaking the numbers into tens and ones work?
4.Sam works out 58 − 37 like this:
37 is close to 40, so 58 − 40 = 18, then add 3 back: 21.
Why does subtracting too much and then adding it back work?
5.Ivy works out 43 − 10 like this:
40 − 10 = 30, and 3 − 0 = 3, then 30 + 3 = 33.
Why does breaking the numbers into tens and ones work here?