A rounded number has about the same value as the number you started with but is less exact.
Rules for rounding
- Identify the place value you are rounding to. For example for rounding currentcy to the nearest cent use 2 decimal places (hundredths).
- Look at the digit to the right of this place:
- If this number is less than 5 (0, 1, 2, 3, 4) you leave your last digit as it is.
- If it is 5 or more (5, 6, 7, 8, 9) you increase the value of your last digit by one.
- Any digits after your place become zeros or are dropped off if they are to the right of the decimal point.
|1. Round to the nearest cent:||Rounded|
|(a) $ 72.3483844||$ 72.35|
|(b) $ 104.2309||$ 104.23|
|(c) $2.3981007||$ 2.40|
|2. Round to the nearest 100:|
Rounding to the nearest whole number
The usual rules for rounding apply in most situations when rounding to a whole number. However, in some situations the correct answer will always require rounding up.
Bottled water is sold in packs of 12. How many packs need to be ordered to ensure that all 147 staff get a bottle of water?
Calculation 147 ÷ 12 = 12.25
Conventional rounding would mean this number would be rounded down to 12.
But notice that 12 x 12 = 144 so 3 staff would miss out.
The correct answer is that that 13 packs should be ordered to ensure every staff member gets a bottle of water.