the following is a question from on of the simulated CAT. I didnt find the answer convincing. Please clarify

Ques) A farmer has an apple orchard consisting of Fuji and Gala apple trees. Due to high winds this year 10% of his trees cross pollinated. The number of his trees that are pure Fuji plus the cross-pollinated ones totals 187, while 3/4 of all his trees are pure Fuji. How many of his trees are pure Gala?

Ans) This problem can be solved using a set of three equations with three unknowns. We'll use the following definitions:

Let F = the number of Fuji trees
Let G = the number of Gala trees
Let C = the number of cross pollinated trees

10% of his trees cross pollinated
C = 0.1(F + G + C) --> why is 'C' included in both LHS and RHS of the equation. Ideally the equation should read as C = 0.1(F + G) because before the cross pollination he has F+G trees. Then owing to high wind 10% of his trees are cross pollinated. Hence no of cross pollinated trees will be 0.1(F + G)

I think I see what the problem is here - there are two ways to interpret the sentence:
(1) 10% of the old trees then cross-pollinated to add new trees (as you're saying), or
(2) 10% of all the current trees are cross-pollinated (as the problem assumes)

You'll solve it differently depending upon how you interpret it. I'll forward to our curriculum director to re-word the problem to make the info more clear.

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Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT