Bunuel wrote:

The ratio of boys to girls at Nat Nowen Elementary school is x : y. If there are z children that attend the school, then in terms of x, y, and z, how many boys attend the school?

A. z/x

B. z/y

C. xz/(x + y)

D. yz/(x + y)

E. (x + z)/(x + y)

Since we have only variables in the question and in the answer, we'll try to plug in easy numbers.

This is an Alternative approach.

Say that x = 1, y = 2 and z = 3. Then there are 1 boy and 2 girls at the school.

So we're looking for the answer that gives 1.

A. gives 3/1 = 3. No!

B. gives 3/2 = 1.5. No!

C. gives 1*3/(1+2) = 1. Looks good but we still need to check the rest.

D. gives 2*3/(1+2) = 2. No!

E. gives (1 +3)/(1+2) = 4/3. No!

(C) is our answer.

_________________

David

Senior tutor at examPAL

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