Number (add/sub)
Hong Kong
Stage 2
Use rounding to estimate solutions for addition and subtraction
Lesson
Why estimate?
Sometimes we need to check that our answer seems reasonable. Other times, we may only need a rough figure for our answer. We have a way to check our answer that helps us find an estimate, so let's work through how to use rounding, to the nearest 10 or 100, to check our answers.
A rough idea
In the next video, we look at how a town works out roughly how many might turn up to the summer fair. This is a great way to see why it can be useful to estimate our answer! We also go over the rules for rounding again, so that we know if we should round up, or down.
Remember!
When we round, we use the next digit to the right to tell us whether to round up or down.