Ramu rides his bike at an average speed of 45 km/hr and reaches his desitination in four hours. Somu covers the same distance in six hours. If Ramu covered his journey at an average speed which was 9 km/hr less and Somu covered his journey at an average speed which was 10 km/hr more, then the difference in their times taken to reach the destination would be (in minutes).  Options:
A) 31 minutes  B) 37 minutes  C) 32 minutes  D) 30 minutes  E) 33 minutes
30 minutes   Distance travelled by Ramu = 45 * 4= 
<gadget id="calculator">45 * 4</gadget>
<output>180</output>
180 km   Somu travelled the same distance in 6 hours.   His speed= 180/6= 
<gadget id="calculator">180/6</gadget>
<output>30</output>
30 km/hr   Hence in the conditional case, Ramu's speed= 45 - 9= 
<gadget id="calculator">45 - 9</gadget>
<output>36</output>
36 km/hr and Somu's speed= 30 + 10= 
<gadget id="calculator">30 + 10</gadget>
<output>40</output>
40km/hr.   Therefore travel time of Ramu and Somu would be 5 hours and 4.5 hours respectively. Hence difference in the time taken= 0.5 hours = 30 minutes.
<result>D</result>
Ramu rides his bike at an average speed of 45 km/hr and reaches his desitination in four hours. Somu covers the same distance in six hours. If Ramu covered his journey at an average speed which was 9 km/hr less and Somu covered his journey at an average speed which was 10 km/hr more, then the difference in their times taken to reach the destination would be (in minutes).