M7MBA wrote:There are twice as many dog owners as cat owners, and the number of owners of both animals is double the number of owners that own only a cat. If 200 owners own both animals, how many owners own only a dog?

A. 100
B. 200
C. 400
D. 600
E. 700

We are given that 200 owners own both animals, and this is double the number of owners who own only a cat. Thus, the number of cat-only owners is ½(200) = 100, and the number of cat owners is 100 + 200 = 300. Since there are twice as many dog owners as cat owners, there are 2(300) = 600 dog owners. Since 200 of them also own a cat, the number of dog-only owners is 600 - 200 = 400.

Answer: C

Hi All,

We're told that there are TWICE as many dog owners as cat owners, the number of owners of both animals is DOUBLE the number of owners that own only a cat and 200 owners own BOTH animals. We're asked for the number of owners who own only a dog. Sometimes GMAT questions are really just about properly organizing the given information and a bit of Arithmetic.

To start, we know that 200 people own BOTH animals (a cat and a dog).
We know that the number who own BOTH animals is DOUBLE those who own JUST a cat. Thus, 200/2 = 100 own JUST a cat.

At this point, we know that there are 300 cat owners (100 own just a cat, 200 own a cat and a dog).
We know that there are TWICE as many dog owners as cat owners; that would be 2(300) = 600 dog owners.
Since there are 200 people who own BOTH animals, there are 600 - 200 = 400 people who own JUST a dog.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich