Use Estimation to Solve Calculations

In this activity, we will be using our rounding skills to estimate the answers to calculations.

This skill is useful for when we need to make approximate calculations for when we don't have a calculator.

Engineers use this skill to estimate the  quantity of materials needed for a building.

We also use rounding when trying to find out what our shopping bill may be as we are going around the supermarket!

Example 1

Round off the values in the calculation to 1 significant figure to work out an estimate to the calculation below.

1.9³ + 8.3 + √120

First, let's round each value to 1 sig. fig.

1.9 → 2

8.3 → 8

120 → 100

Now we have our rounded values we can find an estimate for the calculation.

Remember to apply BIDMAS to your calculations.

2³ + 8 + √100

= 8 + 8 + 10

= 26

Example 2

Round off the values in the calculation to 1 significant figure to work out an estimate to the calculation below.

(2.9 + 8.3)² ÷ 10.1

First, let's round each value to 1 sig. fig.

2.9 → 3

8.3 → 8

10.1 → 10

Now we have our rounded values we can find an estimate for the calculation.

(3 + 8)² ÷ 10

= 11² ÷ 10

= 121 ÷ 10

= 12.1

Great ... let's try the activity!