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2017 Math Kangaroo

Problem 2

Problem 2 · 2017 Math Kangaroo Easy
Arithmetic & Operations careful-counting

A fly has 6 legs and a spider has 8 legs. So 3 flies and 2 spiders together have the same number of legs as 9 chickens and how many cats?

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Answer: C — 4 cats
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Hint 1 of 2
Count the legs on each side, then see how many cats make up the leftover.
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Hint 2 of 2
A cat has 4 legs; divide the missing legs by 4.
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Approach: count legs and divide the difference
  1. 3 flies = 3×6 = 18 legs and 2 spiders = 2×8 = 16 legs, so the left side has 18+16 = 34 legs.
  2. 9 chickens give 9×2 = 18 legs.
  3. The cats must supply 34 − 18 = 16 more legs.
  4. 16 ÷ 4 = 4 cats (C).
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