A) 69.5 km/hr
B) 70 km/hr
C) 79 km/hr
D) 79.2 km/hr
Length of the Bridge = 264 m.
Time taken to pass the bridge = 20 sec.
Time taken to passe the post = 8 sec.
Length of the train = X m (Let.)
To pass the bridge train need to cover Train’s length + Bridge legnth (X +264).
Speed = Distance covered / time taken
Now,
X/8 = (264 + X)/20
20X = 264 *8 + 8X
20X – X = 264 *8
12X = 264 *8
X = (264 *8)/12
X = 176 m.
Speed of the train = 176/8 = 22 m/sec = (22*18)/5 = 79.2 Kmph