Mathematics > Standard Multiple Choice
Read the following SAT test question and then click on a button to select your answer.
A right circular cylinder has height 6 and volume 54 times pi. What is the circumference of its base?
(A) 2 times pi
(B) 3 times pi
(C) 6 times pi
(D) 9 times pi
(E) 18 times pi
The correct answer is C
Explanation
The volume of a cylinder with radius r and height h is equal to pi times (r^2) times h. Therefore, pi times (r^2) times (6) = 54 times pi and r^2 = 9, so the radius of the cylinder is 3. The circumference of a circle with radius r is equal to 2 times pi times r; therefore, the circumference of the base is equal to 6 times pi.