Carry out column addition and subtraction for whole numbers and decimals.
Solve addition and subtraction problems using decomposition, leading to a written algorithm.
Number Framework Stage 7
Using Number Properties
Problem:
"Which is the better way to solve these problems – mentally or using the standard written forms? 997 + 1 234 4 546 – 2 788.”
Discuss why 997 + 1 234 is easy to solve mentally, using strategies such as, 1 000 + 1234 = 2 234, 2 234 – 3 = 2 231.
Doing 4 546 – 2 788 mentally will be beyond most students, so the standard written form is needed for this one.
Examples: A mixture of addition and subtraction problems (Material Master 5–13).