NUM019 · Numbers & number systems · Classes 3–7
Estimation
Estimating means rounding numbers first so the answer is quick and close. It is a good way to check a calculation.
≈ 900Estimation
📐 Formula
a + b ≈ round(a) + round(b)
✏️ Worked example
389 + 512 ≈ 400 + 500 = 900. The exact answer 901 is close.
🌍 Where it is used
Checking a bill, planning a budget, judging if an answer is sensible.
❓ Quick check
Estimate 298 + 403.
🏋️ Practice
EasyEstimate 49 + 32 to the nearest ten.
Answer: 50 + 30 = 80
MediumEstimate 615 − 188 to the nearest hundred.
Answer: 600 − 200 = 400
ChallengeA student got 312 × 9 = 1,808. Is it sensible?
Answer: No: about 300 × 9 = 2,700 (exact 2,808)