Rounding off numbers
Rounding makes a number simpler by changing it to the nearest ten, hundred or thousand. We look at the digit just to the right of the place we are rounding to.
Key idea
If that digit is 5 or more, round up. If it is 4 or less, round down (keep the digit the same). This is "four down, five up".
Worked example
Round 3 476 to the nearest thousand. Look at the hundreds digit: 4. Since 4 is less than 5, round down to 3 000. To the nearest hundred, look at the tens digit 7; since 7 ≥ 5, round up to 3 500.
Rounding to the nearest ten
Round 68 to the nearest ten: the ones digit is 8, so round up to 70. Round 4 350 to the nearest hundred: the tens digit is 5, so round up to 4 400.
Remember
- Only the digit to the right decides up or down.
- 5 always rounds up.
- Digits after the rounding place become 0.