Rounding Numbers
Rounding numbers means changing the digits up or down to make rough calculations easier. The resulting answer in any calculation will be an estimation.
Rounding numbers to the nearest 10
If the unit is less than five, the number needs to be rounded down.
If the unit is 5 or greater, the number needs to be rounded up.
For example:
- 23 would be rounded down to 20
- 25 would be rounded up to 30
- 27 would be rounded up to 30
- 239 would be rounded down to 200
- 251 would be rounded up to 300
- 275 would be rounded up to 300
Rounding numbers to nearest 1000
If the hundreds digit is less than 500, the number needs to be rounded down.
If the hundreds digit is 500 or greater, the number needs to be rounded up.
For example:
- 1239 would be rounded down to 1000
- 1501 would be rounded up to 2000
- 1759 would be rounded up to 2000
Rounding decimal numbers to a whole number
If the first digit after the decimal point is less than 5, the number needs to be rounded down to the whole number.
If the first digit after the decimal point is 5 or greater, the number needs to be rounded up to the whole number.
For example:
- 1.49 would be rounded down to 1
- 1.55 would be rounded up to 2
- 1.79 would be rounded up to 2
Rounding decimal numbers to one decimal place
If the second digit after the decimal point is less than 5, the number needs to be rounded down to one decimal place.
If the second digit after the decimal point in 5 or greater, the number needs to be rounded up to one decimal place.
For example:
- 1.54 would be rounded down to 1.5
- 1.55 would be rounded up to 1.6
- 1.58 would be rounded up to 1.6
Rounding decimal numbers to two decimal places
If the third digit after the decimal point is less than 5, the number needs to be rounded down to two decimal places.
If the third digit after the decimal point is 5 or greater, the number needs to be rounded up to two decimal places.
For example:
- 1.554 would be rounded down to 1.55
- 1.555 would be rounded up to 1.56
- 1.558 would be rounded up to 1.56
