GCSE MATHS PRACTICE
GCSE Rounding and Estimation Questions
Decimal places count digits after the decimal point. Significant figures start at the first non-zero digit; leading zeros do not count. Look at the next digit to decide whether to round up. Estimate by rounding to convenient values before calculating, and use an approximation sign because an estimate is not exact. Use the estimate to check whether a calculator answer is sensible.
Updated 12 October 2026
Worked example
Estimate (19.6 × 4.8) ÷ 0.51 by rounding each number to 1 significant figure.
- Round 19.6 to 20, 4.8 to 5 and 0.51 to 0.5.
- Calculate (20 × 5) ÷ 0.5 = 100 ÷ 0.5 = 200.
- The estimate is approximately 200. An answer near 20 or 2000 would be an unlikely size for the original calculation.
Answer: Approximately 200
Practice questions
- 1
Round 8.746 to 2 decimal places.
- 2
Round 0.004996 to 3 significant figures. Show the precision in your answer.
- 3
Estimate (39.7 × 6.2) ÷ 0.79 by rounding each number to 1 significant figure.
- 4
Estimate (48.7 × 19.4 + 102.3) ÷ 5.1 by rounding each number to 1 significant figure before calculating.
Show answers
- 1. 8.75
- 2. 0.00500
- 3. Approximately 300
- 4. Approximately 220
Common mistakes
- Counting leading zeros as significant — Start counting at the first non-zero digit.
- Dropping precision — Trailing zeros can matter: 0.00500 shows 3 significant figures.
- Treating an estimate as exact — Round as instructed and describe the result as approximate.