Problem 7 · 2019 Math Kangaroo
Easy
Algebra & Patterns
total-then-divide
In an enclosure there is a group of kangaroos. If you add up the ages of all the kangaroos you get 36 years. In two years all the kangaroos together will be 60 years old. How many kangaroos are in the enclosure?
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Answer: A — 12
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Hint 1 of 3
In two years every single kangaroo gets exactly 2 years older.
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Hint 2 of 3
So the whole total grows by 2 for each kangaroo there is.
Still stuck? Show hint 3 →
Hint 3 of 3
The total grew from 36 to 60; ask how many 2s fit into that growth.
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Approach: the total gains 2 years per kangaroo
- In two years the combined age goes from 36 to 60, so it grows by 60 − 36 = 24 years.
- Each kangaroo is responsible for 2 of those extra years, so there must be 24 ÷ 2 = 12 kangaroos.
- There are 12 kangaroos (A).
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