trigonometry
posted by monic .
The wheels of a car have radius 11 in. and are rotating at 800 rpm. Find the speed of the car in mi/h.
mi/h

circumference of wheel
= distance covered in 1 rotation
= 2π(11) = 22π inches
distance covered in 800 rotations
= 800(22π) = 17600π inches
= 17600π/12 ft
= 17600π/(12(5280)) miles
= .87266.. miles per minute
= 52.36 miles/hr