Topic 7 of 10 · Method 4: is my answer sensible?
Estimation
Mr Boston
Before (or after) a big division, a quick estimate tells you roughly what the answer should be. It’s like a sat nav check for your maths.
Method 4 – Estimation
31443 ÷ 47
31,500 ÷ 50 ≈ 630
The real answer is 669.
Estimating helps you know if your answer is sensible.
The sign ≈ means “is approximately equal to”.
How to estimate a division
- Round the divisor to a friendly number. 47 is close to 50.
- Round the dividend to a number that is easy to divide by it. 31443 is close to 31,500, and 315 ÷ 5 = 63.
- Divide the easy numbers. 31,500 ÷ 50 = 630.
- Compare. Is your real answer close? 669 is close to 630, so it is sensible. If you had got 66 or 6,690, you would know something went wrong.
Tayo
An estimate doesn’t need to be exact. It just needs to be the right size: tens, hundreds or thousands.
Practise
Answer as many as you like. Every question is new, and you get a “correct” tick for each one you get right first time.
Quiz: earn your stamp
Printable worksheet
Estimation worksheet. The questions are on the first page, and the answers for grown-ups are on the last page, so you can print just the first page for your child.
Printing is optional. A4 size.