A train, 800 meter long is running with a speed of 78 km/hr. It crosses a tunnel in 1 minute. What is the length of the tunnel ?  Choose the correct choice from the following choices:
A) 650 meter
B) 555 meter
C) 500 meter
D) 458 meter
E) none of these

Rationale: explanation : let length of tunnel is x meter distance = 800 + x meter time = 1 minute = 60 seconds speed = 78 km / hr = 78 * 5 / 18 m / s = 65 / 3 m / s distance = speed * time = > 800 + x = 65 / 3 ∗ 60 = > 800 + x = 20 ∗ 65 = 1300 = > x = 1300 − 800 = 500 so the length of the tunnel is 500 meters . option c
Answer: C