Assistant (BS-16) S&GAD

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 ?

A) 650 m

B) 555 m

C) 500 m

D) 458 m

Let the tunnel be x meters long

To Covert Km/h to m/s we use formual:  [ s x (a/18) ]

So the speed of train in m/s =78km/h=78×5/18= 65/3 m/s

Time taken: 1 min=60 sec

Distance covered would be= x+800

because to cross the tunnel, the train must cover the distance equal to the sum of its length and tunnel’s length:

Now applying Speed=Distance/Time:

65/3 = x+800/60

x+800=65×20

x=1300–800

x=500 m

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