0580
Rounding, Estimation and Bounds
Number
The rule
- Locate the digit sitting in the place value being rounded to
- Look at the single digit immediately to its right, and ignore everything beyond it
- That digit decides the direction: 5 or more rounds up, 4 or less leaves the digit unchanged
- Fill every place between the rounded digit and the decimal point with zeros, since dropping them would change the size of the number
- 4826 to the nearest hundred is 4800
- 4872 to the nearest hundred is 4900
Exam tip
"Correct to the nearest …" is printed in 23 of the 43 papers, and the digit that decides is the next one along, not the whole tail. 3 4 9 to the nearest hundred is 300, because the deciding digit is the 4; reading the 9 and rounding up twice is the standard way this goes wrong.