Math · Stage 3
Round to estimate, then judge if an answer makes sense
Round to the nearest 10 or 100, add or take away the easy way, and use the estimate to check if a big answer is sensible.
✦ Math📘 Stage 3 · S3⏱ ~11 min🧒 Ages 7–8★ Free to start
I can round numbers to the nearest 10 or 100, and use rounding to estimate sums and differences and judge whether an answer is sensible.
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Kavi's Sensible Check 🪧
Kavi counts 372 acorns in one hollow and 280 in another 🌰. "Which hundred signpost is each one nearest?" he hoots. "372 → 400 and 280 → 300, so together it's about 700." A friend guesses the real total is 65. "That can't be right," says Kavi — "my estimate says around 700!"
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What your child will learn
1The nearest hundred signpostYou already round to the nearest 10. Now the big signposts are the hundreds: 0, 100, 200, 300. Every number sits between two hundreds — rounding means hop to the closest one. Tap Hop +100 to travel signpost to signpost.
2Let the tens digit decideTo round to the nearest 100, look at the tens digit. Build 472: the hundreds digit is 4 and the tens digit is 7. The tens digit decides which hundred we land on.
3Round, then addThis is why rounding is so handy. To estimate 372 + 280, first round each to the nearest 100: 372 → 400 and 280 → 300. Now add the easy hundreds. Tap Step → to build 400 + 300.
4Is the answer sensible?An estimate is a quick check. Count the hundreds you can land on: 100, 200, 300, 400. If someone adds 372 + 280 and says 65, your estimate of about 700 shouts "too small!" A sensible answer sits near the estimate.
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A peek inside
Round 372 to the nearest 100.
tens digit is 7 (5 or more) → round up
Try this at home: Round to the nearest 100: 372 → __ · 280 → __ · 650 → __
Ready to play and learn?
Start the free interactive lesson, or print the handout for screen-free play.
Part of Math · Stage 3 · S3 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.