Official Guide Explanation:
Problem Solving #197




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Solution and Metadata

Question: 197
Page: 180
Difficulty: 6 (Moderately Difficult)
Category 1: Word Problems > Geometry Problems >
Category 2: Geometry > Circles > other
Category 3: Word Problems > Rate Problems > Speed

Explanation: If the fan runs at a rate of 300 revolutions per minute, that's 75 revolutions in 15 seconds. The point on the edge of the blade is 10 centimeters from the center; the distance it travels in each revolution is the same as the circumference of a circle with a radius of 10.

c = 2 π r = 20 π

75 revolutions, then, is 75 times that much:

75(20 π ) = 1500 π , choice (B).

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