Question

If two trains of length 30 m 50 m . moves in opposite direction. if they cross each other in 4 second find the velocity of each train of the speed of the longer one is 7 times that of shorter one

Answer 1

Let speed of the faster train be x and speed of the slower train be y

when the trains run in same direction,  speed of the faster train with respect to the slower train = (x-y)

time taken  = 25 sec

distance travelled while crossing = 200+250 = 450 m

450 = 25(x-y)          [∵ distance = speed * time]

x - y = 18 ----(1)

when the trains run in opposite direction, relative speed = x+y

time taken  = 15 sec

distance travelled = 450 m

450  = 15(x+y)

x + y = 30  ----(2)

Solving (1) and (2) for x

adding (1) and (2) gives  2x = 48

x = 24

speed of the faster train = 24 m/s

look at this and accordingly make changes in the value