Bunuel wrote:
A certain zoo has mammal and reptiles and birds, and no other animals. The ratio of mammals to reptiles to birds is 11: 8:5. How many birds are in the zoo?
(1) there are twelve more mammals in the zoo than there are reptiles
(2) if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1
Kudos for a correct solution.
Target question: How many birds are in the zoo? Given: The ratio of mammals to reptiles to birds is 11: 8:5. Given this ratio, we could say that
there are:
11x mammals
8x reptiles
5x birds
for some value of x.
Statement 1: there are twelve more mammals in the zoo than there are reptiles We can write: number of mammals = number of reptiles + 12
Or we can write: 11x = 8x + 12
Solve to get x = 4
Once we know the value of x, we can see that
the number of birds = 5x = (5)(4) = 20Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: if the zoo acquired 16 more mammals, the ratio of mammals to birds would be 3:1 So, (current number of mammals + 16)/(current number birds) = 3/1
Or we can write: (11x +16)/5x = 3/1
Cross multiply to get: 11x + 16 = 15x
Solve, to get x = 4
Once we know the value of x, we can see that
the number of birds = 5x = (5)(4) = 20Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer = D
Cheers,
Brent