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 54π. What is the circumference of its base?

　　(A) 2π

　　(B) 3π

　　(C) 6π

　　(D) 9π

　　(E) 18π

　　Explanation

　　The volume of a cylinder with radius r and height h is equal to π*(r^2)*h. Therefore, π*(r^2)*(6) = 54π and r^2 = 9, so the radius of the cylinder is 3. The circumference of a circle with radius r is equal to 2π*r; therefore, the circumference of the base is equal to 6π.

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（编辑：马菲）