Work through the levels in order. Type your answer and press Check — open the worked solution if you get stuck. Answers like -6, 3/4 or 0.25 are typed exactly as shown. A ⭐ Bonus Challenge at the end is extra credit — skip it if the rest was hard work.
Level 1 · Warm-up
1 Work out 38 217 + 24 906.
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Estimate 63 000. Exact: 63 123.
2 For 71 480 − 19 620, give an estimate (round each number to the nearest thousand) and the exact answer.
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Estimate: 71 000 − 20 000 = 51 000. Exact: 51 860.
3 Work out 245 806 + 138 195.
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6 + 5 = 11, 0 + 9 + 1 = 10, 8 + 1 + 1 = 10, 5 + 8 + 1 = 14, 4 + 3 + 1 = 8, 2 + 1 = 3: 384 001.
Level 2 · Core
4 Work out 40 000 − 18 765.
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10 − 5 = 5, 9 − 6 = 3, 9 − 7 = 2, 9 − 8 = 1, 3 − 1 = 2: 21 235. (Estimate 40 000 − 19 000 = 21 000 ✓.)
5 For 603 000 − 176 428, give an estimate to the nearest ten thousand and the exact answer.
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Estimate: 600 000 − 180 000 = 420 000. Exact: 426 572.
6 A town's population was 1 048 900. It grew by 96 350. What is the population now?
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1 048 900 + 96 350 = 1 145 250. (Estimate 1 050 000 + 100 000 = 1 150 000 ✓.)
Level 3 · Challenge
7 Mia works out 300 000 − 124 875 and writes 185 125.1 A rounded estimate is about 175 000.
2 Mia's answer is wrong.
3 The correct answer is 175 125.
Which statements are correct?
2 Mia's answer is wrong.
3 The correct answer is 175 125.
Which statements are correct?
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300 000 − 125 000 = 175 000 (1 ✓). 185 125 is 10 000 too big, so it is wrong (2 ✓). Redoing the trade: 175 125 (3 ✓). 1, 2 and 3.
8 An odometer read 128 476 km, then 130 052 km after trip 1, then 131 900 km after trip 2. How long was each trip?
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Trip 1: 130 052 − 128 476 = 1 576 km. Trip 2: 131 900 − 130 052 = 1 848 km.
9 Leo adds 47 812 to a number and then subtracts 30 000. The result is 94 250. What number did Leo start with?
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94 250 + 30 000 = 124 250. Then 124 250 − 47 812 = 76 438.