A train covers a distance in 50 minutes, if it runs at a speed of 48kmph on an average. Find the speed at which the train must run to reduce the time of journey to 40 minutes. Choose the correct choice:  A) 50 km/hr  B) 60 km/hr  C) 65 km/hr  D) 70 km/hr  E) None of these
Explanation:   We are having time and speed given, so first we will calculate the distance. Then we can get new speed for given time and distance.   Lets solve it.   Time = 50/60 hr = 5/6 hr   Speed = 48 mph   Distance = S × T = 48 × 5/6 = 40 km   New time will be 40 minutes so,   Time = 40/60 hr = 2/3 hr   Now we know,   Speed = Distance/Time   New speed = 40 × 3/2 kmph = 60kmph   Answer: 60 km/hr
<result>B</result>
A train covers a distance in 50 minutes, if it runs at a speed of 48kmph on an average. Find the speed at which the train must run to reduce the time of journey to 40 minutes.