A train passes two bridges of length 1000 m and 600 m in 120 seconds and 80 seconds respectively. The length of the train.

Question: A train passes two bridges of length 1000 m and 600 m in 120 seconds and 80 seconds respectively. The length of the train.

Solution:
Distance covered in 120 second = 1000 + length of train(l)
Distance covered in 80 seconds = 600 + l
So, distance covered in 40 seconds = (1000 + l) - (600 + l)
= 400 m

Speed = 400/40 = 10 m/s

∴ Distance covered in 80 second = 80 × 10 = 800 m
So, 600 + l = 800
∴ Length of the train (l) = 200 m