Question

a train moving on linear path travels a distance D at a constant speed of 30 km/h,then it travels the same distance in opposite direction and reaches initial position at a constant speer of 45km/h.What is the average of the train?

Answer 1

here,
let time taken by train to cover distance D be t
now, t = D/30
again, train travels distance D
so, time taken by train to cover distance D with speed, v = 45km/h
t = D/45
now, average speed = total distance /total time
= D+D/(D/30+D/45)
= 2D/ D/18
= 18 x 2 = 36 km/h
HOPE THIS HELPS YOU ;-)

Answer 2

hi here is Ur answer

TRIP 1

distance covered =D AS GIVEN

TIME =D/30

SIMILARLY in TRIP 1

TIME =D/45

AV SPEED=TOTAL DISTANCE/TIME

=2D/D/30+D/45

=36