Rounding numbers to decimal places involves counting the required number of decimal places after the decimal point; then checking the next decimal place to determine the rounding required. If the next decimal place is 5 or more, the number is rounded up.
For example, giving 0.54603 to two decimal places would be 0.54: but check the following (third) decimal place. It is a 6, so the number is rounded up to 0.55.
Decimal Places are sometimes abbreviated to dp: the number 23.456 which is accurate to three decimal places will be shown as 23.456 (3dp).
Examples of rounding to decimal places:
| Number | 0.52064 | 23.8569 | 0.000543 | ||
| 1 decimal place | 0.5 | 23.9 | 0.0 | ||
| 2 decimal places | 0.52 | 23.86 | 0.00 | ||
| 3 decimal places | 0.521 | 23.857 | 0.001 |
An experiment in a physics lab has shown that the force required to move an object was 2.466 Newtons. What is this force measured to 1 decimal place (1 dp)?
The number is 2.4 to 1dp; check the following digit (6). As it is greater than 5 then round the number up.
Answer: 2.5 Newtons
Charlie bought a book for £10. It had `frac(1)(3)` off because it was in a sale. How much did Charlie pay?
The purchase price is 10 x `frac(2)(3)` = 6.66666 recurring, or `6.dot6`. Round to 2 decimal places (for pence) gives 6.67. The implication to round to 2 decimal places is given by the use of pounds and pence.
Answer: £6.67