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.
Level 1 · Warm-up
1 Work out 2.3 + 1.4. (as a decimal)
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Tenths: 3 + 4 = 7. Units: 2 + 1 = 3. So the answer is 3.7.
2 Work out 5.6 + 2.7. (as a decimal)
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Tenths: 6 + 7 = 13, so write 3 and carry 1. Units: 5 + 2 + 1 = 8. The answer is 8.3.
3 Work out 8.9 − 3.4. (as a decimal)
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Tenths: 9 − 4 = 5. Units: 8 − 3 = 5. So the answer is 5.5.
Level 2 · Core
4 Work out 3.4 + 12.75. (as a decimal)
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3.40 + 12.75: hundredths give 5, tenths give 11 so carry 1, and units give 2 + 3 + 1 = 6. The answer is 16.15.
5 Work out 0.8 − 0.35. (as a decimal)
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0.80 becomes 7 tenths and 10 hundredths. Then 10 − 5 = 5 and 7 − 3 = 4, giving 0.45.
6 Work out 5 − 2.6. (as a decimal)
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5.0 − 2.6: trade a unit for 10 tenths, so 10 − 6 = 4 tenths and 4 − 2 = 2 units, giving 2.4.
Level 3 · Challenge
7 Work out 9.4 − 0.86. (as a decimal)
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9.40 − 0.86: trade a tenth to get 3 tenths and 10 hundredths. Then 10 − 6 = 4, 3 − 8 needs another trade giving 13 − 8 = 5, and 8 − 0 = 8. The answer is 8.54.
8 You pay for a $37.85 pair of shoes with a $50 note. How much change do you get? (as an amount of money)
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50.00 − 37.85 = $12.15. Estimating 50 − 38 = 12 first tells you the answer should be close to $12.
9 Three lengths of timber measure 1.25 m, 0.5 m and 2.75 m. What is their total length? (as a decimal number of metres)
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1.25 + 0.50 + 2.75: hundredths give 25 + 50 + 75 = 150 hundredths, which is 1.50. Adding the whole metres 1 + 0 + 2 = 3 gives 4.5 m.