Rounding

Rounding simplifies a number. Imagine walking into a shop an 5 items are 99p. Your brain will round each item to a pound and realise the total cost is about £5!

To the nearest...

If we round 236 to the nearest hundred, we will either get 200 or 300. If the number is 250 or more, it will round up to 300, if less then it will round down to 200. 236 is closer to 200, so will round to 200.

Decimal places

Decimals can be very long (or can go on forever!) To round a decimal we can use decimal places. We count the number of digits past the decimal place we want.

Rounding 0.1351 to 2 decimal places will either give us 0.13 or 0.14. We look at the 'next digit' to work out what will happen. If the 'next digit' is 5 or more, it will round up, if less then it will round down. 5 is 5 or more, so will round up to 0.14.

Significant figures

Some numbers, like distances in space, can get very big. Significant figures will work with any number, even if its not a decimal. The rules are the same for decimal places, but we do not start counting at the decimal point any more. Significant figures count the number of digits after the first non-zero digit.

Rounding 36781 to 2 significant figures will either give us 36000 or 37000. We look at the 'next digit' to work out what will happen. If the 'next digit' is 5 or more, it will round up, if less then it will round down. 7 is 5 or more, so will round up to 37000.