The figure above represents two tangential wheels touching one another at exactly one point. The larger wheel has a circumference of 6π and the smaller wheel has a circumference of 4π. If

*x* and

*y* are the centers of the wheels, what is the distance from point

*x* to point

*y*?

A. 5

B. 6

C. 10

D. 12

E. 15

(A) This question is essentially just asking for the sum of the two radii, since the wheels are touching.

Since circumference = 2π

*r*, radius = circumference/2π. Thus, the smaller wheel has a radius of 4π/2π = 2 and the larger wheel has a radius of 6π/2π = 3.

The distance between

*x* and

*y* is 2 + 3 = 5. The correct answer is choice (A).

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**What is the difference between the number of revolutions the two gears make per minute?**