Problem 4 · 2015 Math Kangaroo
Easy
Arithmetic & Operations
careful-counting
Mr Bauer has 10 ducks. 5 of these ducks lay an egg every day. The other 5 lay an egg every second day. How many eggs will the 10 ducks have laid after 10 days?
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Answer: A — 75
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Hint 1 of 2
Work out the two groups of ducks separately, then add their egg counts.
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Hint 2 of 2
An every-second-day duck lays once every two days, so in 10 days it lays only 5 eggs.
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Approach: count each group's eggs over 10 days and add
- The 5 everyday ducks each lay 10 eggs in 10 days: 5 × 10 = 50 eggs.
- The other 5 ducks lay every second day, so 5 eggs each in 10 days: 5 × 5 = 25 eggs.
- Altogether 50 + 25 = 75 eggs.
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