Rounding and estimating
When do you round up, and when down? And how do you quickly see whether an answer is reasonable? Try it yourself.
Your numbers
Answer
Rounded to hundreds
3,500
How to work it out
- 1Look at the digit right after: 8
- 2It is 5 or more — round up.
- 33,486.749 ≈ 3,500
The formula
0, 1, 2, 3, 4 → ned · 5, 6, 7, 8, 9 → op
The rounding rule: the digit right after decides.
Estimate: round first, calculate afterwards
An estimate tells you whether the answer is reasonable — e.g. whether 48 · 21 is close to 1,000.
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