A train passes two bridges of length 800 m and 400 m in 100 seconds and 60 seconds respectively. The length of the train is:

Answer: Option C

1^st Method:
Let length of the train be x m and speed of the train is s kmph.
Speed, s = $$\frac{x+800}{100}$$ . . . . . (i)
Speed, s = $$\frac{x+400}{60}$$ . . . . . (ii)
Equating equation (i) and (ii), we get,
Or, $$\frac{x+800}{100}$$  = $$\frac{x+400}{60}$$
Or, 5x + 200 = 3x + 2400
Or, 2x = 400
Or, x = 200m

2^nd Method:
As in both cases, the speed of the train is constant, and then we have;
Time α distance
$$\begin{array}{rl}& \frac{100}{60}=\frac{x+800}{x+400}\\ & \text{or,}x=200\text{m}\end{array}$$