Question

on a 100 meters track a train travels the first 30 kilometer at a uniform speed of 30km/h. how fast must the train travels the next 70 kilometers so as to average 40km/h for the entire trip.

please give the answer with steps. only for brilliant brainly userz.

Answer 1

Given:
Distance 1 = 30 Km
Distance 2 = 70   Km

Speed = distance /time and
avg speed = total distance / total time taken

when the train acquired a speed of 30km/h, the time taken is -

30 = 30/t .... 30/30
T1 = 1 second

As we know that the avg speed = total distance / total time taken
   [ where time 2 = time for the second part, for 70 km ] 


40 = 100 / 1 + time 2                              

40 + 40 time 2 = 100

40time2 = 100 - 40
40time2 = 60 

Time2 = 1.5 hours

Speed for the second part is
= distance 2 /time 2

s = 70 / 1.5

s = 46.666.. km/h or 46.7km/h (approx)
Therefore, train has to travel with speed of
46.7 k. / h