Lesson

Do you remember how to estimate the answer to an addition problem ?

Choose the right answer.

143 + 33 will be in the:

A

100s

B

200s

Worked Solution

Idea summary

Once we round the numbers in our question, we can then add them together to get an estimate of our answer.

Let's see how we can estimate the answer to a subtraction problem, by rounding our numbers first.

Choose the right answer.

46 - 2 will be in the:

A

40s

B

30s

Worked Solution

Idea summary

When we need to solve a subtraction problem, we can still round our numbers to the nearest 10,\,100, or 1000, just as we would for addition. We don't need the exact answer so this gives us an idea of what our answer should be close to.

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers