Learn how to estimate calculations

Estimations are used to quickly estimate the answer of an expression.


Example

134+159130+160290

You look at the last digit in each number

If the last number is < 5, then round off to the nearest 0

If the last number is ≥ 5, then round off to the nearest 10

You can estimate products and quotients as well.


Example

Round off the factors and multiply the factors.

55.87.42567=8

55.856

7.427


Example

Multiply the two decimal numbers.

First we multiply the two numbers without estimating this to be able to compare the different results.

3.57.3=x3.57.3_105+2450_25.55

Now if we would have estimated the answer instead we would have round off 3.5 to 4 and 7.3 to 7. This would have given us an estimate of

3.57.347=28

As we can see the answers are pretty similar, but not identical.


Video lesson

Estimate