Q.
A. 45 m
B. 50 m
C. 54 m
D. 72 m
E. None of the above
Correct choice: B
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
9y - 5 = x and 10(9y - 10) = 9x
9y - x = 5 and 90y - 9x = 100.
On solving, we get: x = 50.
Length of the train is 50 m.