Q.
A. 66 km/hr
B. 72 km/hr
C. 78 km/hr
D. 81 km/hr
E. None of the above
Correct choice: D
Explanation:
Let the speed of the train be x m/sec.
Then, (x - 1.25) x 8.4 = (x - 1.5) x 8.5
8.4x - 10.5 = 8.5x - 12.75
0.1x = 2.25
x = 22.5