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2009 Math Kangaroo

Problem 7

Problem 7 · 2009 Math Kangaroo Easy
Algebra & Patterns substitutionratio

In a park there are some cats and dogs. The number of cats’ feet is double the number of dogs’ noses. The number of cats is … ? … the number of dogs.

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Answer: B — half the size
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Hint 1 of 2
A cat has 4 feet and a dog has 1 nose; turn the sentence into an equation.
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Hint 2 of 2
Write 4 x (cats) = 2 x (dogs) and solve for the ratio.
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Approach: translate to an equation and compare counts
  1. Cat feet = 4 x (cats); dog noses = 1 x (dogs).
  2. 'Cat feet is double the dog noses' gives 4 x cats = 2 x dogs, so dogs = 2 x cats.
  3. Thus the number of cats is half the number of dogs.
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