1.  A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:
A. 130
B. 360
C. 500
D. 540

Answer: Option C

Explanation:

Speed = ( 78 x 5 ( m/sec = ( 65 ( m/sec.
18 3

Time = 1 minute = 60 seconds.

Let the length of the tunnel be x metres.

Then, ( 800 + x ( = 65
60 3

=> 3(800 + x) = 3900

=> x = 500.