A train 400 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 answer
A) 298 m	B) 500 m	C) 900 m	D) 967 m	E) 1181 m
Speed = 78 * 5/18 = 65/3 m/sec.   Time = 1 min = 60 sec.   Let the length of the train be x meters.   Then, (400 + x)/60 = 65/3   x = 900 m.   Answer: 900 m
<result>C</result>
A train 400 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?