Round each number to make it easier. Then compute. The answer will be close — that's the point.
The six facts you need
Every estimation question uses one of these. You don't need to remember anything else.
1 · What estimation isFinding an answer that is CLOSE, not exact. Fast and rough.
2 · How to estimateRound each number to make it easier — then do the calculation.
3 · Round to 1 sig figKeep the first digit; the rest become zeros. So 274 → 300 · 4.7 → 5 · 0.032 → 0.03.
4 · Add / SubtractRound each number; then add or subtract.
5 · Multiply / DivideRound each number so they multiply or divide easily (like 80 × 40 or 600 ÷ 30).
6 · The ≈ symbol≈ means "approximately equal to". Use it when writing estimates.
Worked example 1 - round to 1 sig fig
Round 274 to 1 significant figure.
Read it. Round 274 to 1 sig fig.
The fact. Keep the first digit; the rest become zeros. Look at the next digit for the up-or-down rule.
First digit of 274: 2 (in the hundreds).
Next digit: 7. 7 is 5 or more, so round UP.
2 hundreds → 3 hundreds → 300.
Answer: 300
Watch out1 sig fig = round to the BIGGEST column of the number.
Worked example 2 - round a decimal to 1 sig fig
Round 4.7 to 1 significant figure.
Read it. Round 4.7 to 1 sig fig.
The fact. For a number between 1 and 10, 1 sig fig = nearest whole number.
4.7. First digit: 4 (ones).
Next digit: 7. Round UP.
4 → 5.
Answer: 5
Watch outFor 4.7 the biggest column is ones. Round to a whole number.
Worked example 3 - estimate addition
Estimate 274 + 189 by rounding each to 1 sig fig.
Read it. Estimate 274 + 189.
The fact. Round each to 1 sig fig, then add.
274 → 300.
189 → 200.
300 + 200 = 500.
Answer: ≈ 500
Watch outThe estimate is NOT the exact answer. It just tells you the right ballpark.
Worked example 4 - estimate subtraction
Estimate 856 − 439 by rounding each to 1 sig fig.
Read it. Estimate 856 − 439.
The fact. Round each, then subtract.
856 → 900.
439 → 400.
900 − 400 = 500.
Answer: ≈ 500
Watch outEstimates can be over or under the exact answer. They're just close.
Worked example 5 - estimate multiplication
Estimate 82 × 39 by rounding each to 1 sig fig.
Read it. Estimate 82 × 39.
The fact. Round each, then multiply.
82 → 80.
39 → 40.
80 × 40 = 3200.
Answer: ≈ 3200
Watch outRounded numbers with lots of zeros are easy to multiply. That's the point.
Worked example 6 - estimate division
Estimate 621 ÷ 29 by rounding each to 1 sig fig.
Read it. Estimate 621 ÷ 29.
The fact. Round each so they divide easily, then divide.
621 → 600.
29 → 30.
600 ÷ 30 = 20.
Answer: ≈ 20
Watch outRound the numbers so they divide EASILY. 600 ÷ 30 is much simpler than 621 ÷ 29.
Worked example 7 - real-world total
You buy 3 items at £6.75 each. Estimate the total.
Read it. Estimate the total of 3 items at £6.75 each.
The fact. Round the price. Keep small counts as they are.
£6.75 → £7.
3 × £7 = £21.
Answer: ≈ £21
Watch outSmall numbers like 3 don't need rounding. They're already easy.
Worked example 8 - is it enough
You have £20. Is that enough for 3 items at £6.75 each?
Read it. Estimate the cost, then compare with what you have.
The fact. Estimate first. Then compare.
Estimate cost: 3 × £7 = £21.
You have £20.
£20 < £21.
Answer: NO — not enough
Watch outThe exact cost is 3 × £6.75 = £20.25. Even the exact answer confirms £20 is not enough.
Practice · Section A
Rounding to 1 sig fig
Whole numbers · Decimals
Practice · Section B
Estimating calculations
Add, subtract, multiply, divide
Practice · Section C
Real-world estimation
Money totals · Is it enough?
Ready for more? 100 questions
When you have done these 12, you are ready for the bigger practice paper.
It has 100 questions. They start very easy and get harder near the end. Every question is still Grade 2 — nothing harder. You can stop at any time and come back.