Speed of train 1 = 48 kmph
Let the length of train 1 = 2x meter
Speed of train 2 = 42 kmph
Length of train 2 = x meter (because it is half of train 1's length)
Distance = 2x + x = 3x
Relative speed = 48 + 42 = 90 kmph
=90× m/s = 25 m/s
Time = 12 s
=speed⇒=25 ⇒
x=25×=100 meter
Length of the first train = 2x = 200 meter
Time taken to cross the platform = 45 s
Speed of train1 = 48 kmph =
=m/s
Distance = 200 + y where y is the length of the platform
⇒
200+y=45×=600⇒
y=400 meter