# How to round a number off to an appropriate degree of accuracy. What does this mean?

If a maths problem asks you to round your answer to an appropriate degree of accuracy then you need to look at the numbers in the question and see what these numbers have been rounded to. So for example, if the numbers in the question have been rounded to 3 decimal places then it would be a good idea to round your answer off to 3 decimal places.

Also, if the question is based around a money problem then your answer should normally be given to 2 decimal places or to the nearest whole number.  Rounding money off to 1 decimal place would not really be appropriate.

Example 1

Work out the area of a rectangle of side length 4.3cm by 8.8cm. Give your answer to an appropriate degree of accuracy.

All you need to do is multiply the two side lengths together.

4.3 × 8.8

Now since the numbers in the question are given to 1 decimal place then you need to round the answer to 1 decimal place.

= 37.8 cm²

Example 2

A plane travels 3560 miles in 7.53 hours. Calculate the average speed of the plane flight. Give your answer to an appropriate degree of accuracy.

To work out the average speed of the plane you need to divide the distance by the time.

3560 ÷ 7.53 = 473 mph (rounded to 3 significant figures).

The answers was rounded to 3 significant figures because 3560 and 7.53 are both given to 3 significant figures.

Sometimes, it might not be clear what to round a number off to, as the numbers in the question may be given to different degrees of accuracy. In these cases, it would be wise to round your answer off to 3 significant figures, as this is usually the most commonly suggested way of rounding on the front of many exam papers.