AR020 · Arithmetic operations · Classes 4–8
Arithmetic estimation
To estimate a product or quotient, round each number to one significant figure, then calculate. The estimate shows roughly how big the answer should be.
≈ 50 × 20Arithmetic estimation
📐 Formula
a × b ≈ round(a) × round(b)
✏️ Worked example
48 × 21 ≈ 50 × 20 = 1000; the exact answer is 1008.
🌍 Where it is used
Checking calculator answers and quick budgeting.
❓ Quick check
Estimate 61 × 39.
🏋️ Practice
EasyEstimate 29 × 11.
Answer: 30 × 10 = 300
MediumEstimate 812 ÷ 39.
Answer: 800 ÷ 40 = 20
ChallengeIs 73 × 48 = 2,504 sensible?
Answer: No: ≈ 70 × 50 = 3,500 (exact 3,504)