Bunuel wrote:

Initially, how many black chips are in a box containing only red chips and black chips, all identical except for color?

(1) Initially, the ratio of red chips to black chips in the box is 3/25.

(2) If 12 red chips and 80 black chips are removed from the box, the probability of randomly drawing a red chip from the box is 1/11.

We'll translate our data into equations to help us understand what we need to do.

This is a Precise approach..

(1) So r/b = 3/25. This is one equation with two variables and is insufficient.

Insufficient.

(2) We can write this as an equation to help us out:

(r - 12) / (r + b - 92) = 1/11

This is an equation with two variables and has infinite solutions.

Insufficient.

Combined:

We now have two equations with two variables we can solve. (But we won't bother!)

Sufficient

(C) is our answer.

_________________

David

Senior tutor at examPAL

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