Rounding to a given number of decimal places

In many calculations you will be expected to round off your answer to a given number of decimal places.

Round \(3.168\) to two decimal places.

\(3.168\) is correct to three decimal places as there are \(3\) digits after the decimal point.

If the number at the next decimal place is five or more add 1 to the previous decimal place.

With \(3.168\) the number at the third decimal place is five or more.

So, \(3.168\) rounds up to \(3.17\) (to two decimal places).

Round \(17.839\) to one decimal place.

If the number at the next decimal place is smaller than five then leave the previous decimal place as it is.

With \(17.839\) the number at the second decimal place is smaller than five.

So, \(17.839\) rounds down to \(17.8\) (to one decimal place).

Now try these questions:

Question

Express \(\frac{9}{{13}}\) as a decimal correct to \(3\) decimal places.

Find \(\sqrt {8.9}\) as a decimal correct to \(1\) decimal place.