Question

After covering a distance of 30 km with a uniform speed there is some effect in a train engine and therefore its speed gets reduced to 4/5 of its original speed.Consequently, the train reaches its destination late by 45 minutes.If the defect in engine would have occurred after covering 18km more distance,the train would have reached 9 nimutes earlier.The original speed of the train is
a) 120 k /hr
b)90km/hr
c)30km/hr
d)20km/hr​

Answer 1

Train proceeds at 4/5 S where S is his usual speed means 1/5 decrease in speed which

Now the main difference comes in those extra

18km and the change in difference of time = (45-36) min = 9 min.

Thus,

1/4*T = 9 min where T is the time required to cover the distance of 18 km.

T = 36 min = 36 /60 hours = 0.6 hours.

Speed of the Train = 18/0.6 = 30 kmph