SAT Math Multiple Choice Practice Question 40: Answer and Explanation
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?
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.