Add and subtract the same amount to both numbers in addition or subtraction to give a zero effect. Objective is to make a nice number, that is easier to work with. Example
7 + 8 =
(7+3) + (8-3)=
10 + 5 = 15
or
In subtraction, make the subtraend a nice number, (multiple of 10), subtract from the minuend. Then add the compensating number.
23 - 18
23 -( 20) + 2 =
3+2=5
7 + 8 =
(7+3) + (8-3)=
10 + 5 = 15
or
In subtraction, make the subtraend a nice number, (multiple of 10), subtract from the minuend. Then add the compensating number.
23 - 18
23 -( 20) + 2 =
3+2=5