Estimating and rounding to tens and hundreds
Round numbers to the nearest ten or hundred and estimate sums and differences without an exact calculation.
- Germany: grade 4
- Iran: grade 2
Guide
Sometimes we do not need the exact number. We say "about 300 pupils". This is an estimate.
One way: drop the ones digit and write 0 in its place. 731 becomes 730. To round to hundreds, drop the tens and ones and write zeros: 124 becomes 100.
Another way: look at the number on the line and say which ten or hundred it is nearest to. 47 is closer to 50 than to 40.
To estimate a sum, simplify each number first, then add the easy numbers. Use the way the question asks for.