Indian Institute of Foreign Trade 2012 Solved Paper

Speed of train 1 = 60 km/hr = 50/3 m/s
Speed of train 2 = 48 km/hr = 40/3 m/s
Thus, their relative speed = 90/3 = 30 m/s
Let, Length of train 1 = l
Thus, the length of train 2 will be 0.5 l
Time taken by them to cross each other = 15 s
Thus, 15×30=1.5l
Thus, l=300
Train 1 takes 51s to cross a bridge
Let the length of the bridge be b
Thus,

50×51

3

=300+b
Hence, 850=300+b
Hence, b=550m
Thus, option A is the correct answer.