S = (100 + 300)/45 = 400/45 * 18/5 = 32 kmph
A train 100 meters long completely crosses a 300 meters long bridge in 45 seconds. What is the speed of the train is?

[a] 25 kmph
[b] 32 kmph
[c] 40 kmph
[d] 38 kmph
[e] 92 kmph