SAT Math Multiple Choice Practice Question 40: Answer and Explanation

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Question: 40

18. A bicycle has a front wheel radius of 18 inches. If the bicycle wheel travels 50 revolutions, approximately how many feet has the bicycle rolled?

A. 2,827
B. 471
C. 353
D. 236
E. 235

Correct Answer: B


B. Ah, yes, an SAT classic. Every time a wheel rotates, it covers the equivalent of one circumference of distance. The circumference equals 2πr, but you have to be careful about units. The wheel has a radius of 18 inches, but your answer needs to be in feet. The circumference is 2 × 18 × π inches = 36π inches = 3π feet = about 9.4248 feet. Therefore, 50 revolutions covers 50 × 9.4248 = 471 feet.

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