Bunuel wrote:

If 25 percent of the surface area of right circular cylinder X is shaded and 40 percent of the surface area of right circular cylinder Y is shaded, what is the of the shaded portion of right circular cylinder X?

(1) The area of the shaded portion of the surface area of cylinder X is 75 percent of the area of the shaded portion of the surface area of cylinder Y

(2) The surface area of cylinder Y is 10

Let A1 be surface area of right circular cylinder X and A2 be that of other cylinder.

Statement 1) A1 * 0.25 = 0.75 * .40 * A2

SO we get a relationship between A1 and A2.

Not suff.

Statement 2) A2 = 10.

Not suff.

1+2 together. sufficient as we can back-calculate the req information.

Hence C.

Kudos! if you liked the explanation....