The volume V of a right circular cylinder is V =πr2h, where r is the radius of the base and h is the height of the cylinder. If

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问题 The volume V of a right circular cylinder is V =πr2h, where r is the radius of the base and h is the height of the cylinder. If the volume of a right circular cylinder is 45π and its height is 5, what is the circumference of its base?

选项 A、3
B、9
C、3π
D、6π
E、9π

答案D

解析 You are given that the volume of the right circular cylinder is 45π and the height is 5. It follows that πr2h= 45π, or r2h= 45. Since h = 5 and r2h= 45, it follows that r2= 9, or r = 3. Therefore the circumference of the circular base is 2πr = 2π(3)= 6π, and the correct answer is Choice D.
This explanation uses the following strategy.
Strategy 1: Translate from Words to an Arithmetic or Algebraic Representation
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