The diameter of the driving wheel of a bus is 140 cm. How many revolution, per minute must the wheel make in order to keep a speed of 66 kmph ?  Choose the correct choice from the following options.
A) 33 B) 250 C) 138 D) 278 E) 288
Explanation:   Circumference = No.of revolutions * Distance covered   Distance to be covered in 1 min. = (66 X1000)/60 m = 1100 m.   Circumference of the wheel = 2 x (22/7) x 0.70 m = 4.4 m.   Number of revolutions per min. =(1100/4.4)= 
<gadget id="calculator">(1100/4.4)</gadget>
<output>250</output>
250.   Answer: 250) 250
<result>B</result>
The diameter of the driving wheel of a bus is 140 cm. How many revolution, per minute must the wheel make in order to keep a speed of 66 kmph ?