Estimating
You learn to work out roughly how much a sum is.
How to work it out
- Round the numbers to numbers that are easy to work with.
- Calculate with the rounded numbers.
- The result is roughly the answer.
About how much is 398 + 512?
- Round 398 to 400 and 512 to 500.
- Those numbers are easy to add.
- 400 + 500 = 900.
- So about 900.
More examples
About how much is 49 × 21?
50 × 20 = 1000.
About how much is 812 ÷ 39?
800 ÷ 40 = 20.