Rounding to a given number of places

Counting decimal places

Decimal places are counted from the decimal point:

Diagram of the number 5.743

So, the number 5.1492 has four decimal places, while 4.34 has two decimal places.

curriculum-key-fact
To round a number to a given number of decimal places, look at the number in the next decimal place:
  • If it's less than 5, round down
  • If it's 5 or more, round up

Example

Round 9.6371 to 2 decimal places

This means we need 2 digits after the decimal point.

Diagram of the number 9.6371 with an arrow pointing towards the 3rd digit after the decimal point

Because the next digit 7, is more than 5, we round the 3 up.

9.6371 = 9.64 ( 2 decimal places)

Question

Q1. Round 7.2648 to 2 decimal places.

Q2. Round 8.352 to 1 decimal place.

A1.

Diagram of the number 7.2648

To round to two decimal places, look at the number in the third decimal place. It's a {4}, so round down.

Therefore, 7.2648 = 7.26 ( 2 decimal places)

A2.

Diagram of the number 8.352

To round to one decimal place, look at the number in the second decimal place. It's a {5}, so round up.

Therefore, 8.352 = 8.4 ( 1 decimal place)

curriculum-key-fact
To round a number to a given number of decimal places, the answer must have that number of decimal places - even if you have to add some zeros.

For example, rounding 3.40021 to two decimal places gives 3.40.

You need to write both decimal places, even though the second number is a zero, to show that you rounded to two decimal places.

Remember to look at the number after the one you're interested in. If it's less than 5, round down. If it's 5 or more, round up.