Mental Sums (subtraction)

[releeps]

Hi all,
I am teaching My Pals P3 maths mental sums on subtraction. I have some queries regarding the teaching of mental sums.

Example 1: 83-48 = ____
First step: draw number bonds for 48, that will give 50 and 2
second step: 83-50= 33
third step: 33 + 2 = 35

Example 2: 82-43 = ____
First step: draw number bonds for 43, that will give 40 and 3
second step: 82-40= 42
third step: 42 - 3 = 39

How do I explain clearly to the children when they should add or subtract in the third step? In example 1, addition is required, however example 2 required subtraction.
Thanx in advance!

[Unregistered]

Example 1: 83-48 = ____
First step: draw number bonds for 48, that will give 50 and 2
second step: 83-50= 33
third step: 33 + 2 = 35

Isn't it just easier to add 5 to 83, then subtract 5 from the answer?

83 + 5 = 88
88 - 48 = 40
40 - 5 = 35

[Tachizuno]

The latter method is easier, from what I could imagine...

Add 5, and then subtract 5 from the answer in that problem.

There are many ways to solve a problem.