Problem 6 · 2014 Math Kangaroo
Medium
Logic & Word Problems
balance-scalework-backward
How many ducks weigh the same as a crocodile?
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Answer: B
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Hint 1 of 3
The scales are a trade game: whatever sits on one side weighs the same as whatever sits on the other.
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Hint 2 of 3
Trade the big heavy animals away, one scale at a time, until everything has become ducks.
Still stuck? Show hint 3 →
Hint 3 of 3
Keep swapping until only ducks are left, then just count the ducks.
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Approach: use each balanced scale to trade animals until everything turns into ducks, then count
- One scale shows the crocodile balancing the lighter animals, so we may swap the crocodile for them.
- Another scale shows each of those animals balancing 2 ducks, so swap each one for its 2 ducks.
- After every trade, count the ducks that are left.
- The ducks needed to balance one crocodile come to 6 — choice B.
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