When we want to estimate the result of a calculation, we can (in our head) find the result of the calculation if the numbers were rounded.

To start off with, let us round the numbers in the calculations we look at to one significant figure, in order to estimate the answer.

Example

Estimate 3.8 x 5.2

Exercise

Let’s complete exercise 7E on page 102 of the textbook, rounding each of the numbers to one significant figure for our estimates:

The answers are below:

We won’t always round to one significant figure though. We typically have to look at the numbers and decide what would be sensible. Let’s try this below:

Example

Exercise

Let’s complete exercise 7F from page 103 of the textbook:

The answers are below: