A train 850 m long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 min, then the length of the tunnel is?
Choose the correct choice from the following answers.
A) 510  B) 450  C) 500  D) 520  E) 589
Speed = 78 * 5/18 = 65/3 m/sec.   Time = 1 min = 60 sec.   Let the length of the train be x meters.   Then, (850 + x)/60 = 65/3   x = 450 m.   Answer: Option 450
<result>B</result>
A train 850 m long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 min, then the length of the tunnel is?