The tires on a car are 25 inches in diameter. If the car is moving at a constant speed of 65 miles per hour, how many rotations per second is the front left tire making? Express your answer as a decimal to the nearest tenth. (1 mile = 5280 feet)

Answer 1

distance covered in one rotation
= 25π inches

65 miles/hr
= 65*12*5280 inches/hour
= 65*12*5280/3600 inches/sec

number of rotations
= 65*12*5280/3600 ÷ (25π)
= 14.56.. / sec
or appr 15 rotations per second

check:

distance in 1 second = 14.56*25π
= appr 1143.5 inches
= 4116743.013 inches per hour
= 4116743.013/(12*5280) miles/hr = 64.97
not bad