Question

The radius of the wheel of a bus is 70cm. how many revolutions per minute must a wheel make in order to move at a speed of 66km per hour

Answer 1

radius of wheel = 70cm 
we need  to find no. of revolutions so first we take the circumference
circumference of circle=$2 \pi r$
 = 2 * 22/7 * 70
= 440 cm
we need to convert it into km
so,
=0.0044 km
distance= speed *time
 1min =1/60 hr
distance =  66 * 1/60
=1.1 km
number of revolutions = distance / circumference of wheel
                                   = 1.1/ 0.0044
                                    = 250