Question

A train running at a speed of 72 km/ hr, passes an electric pole in 12 seconds. How much time will it take to cross a tunnel 80m long?​

Answer 1

Question:

____________

A train running at a speed of 72 km/ hr, passes an electric pole in 12 seconds. How much time will it take to cross a tunnel 80m long ?

Answer:

__________

Speed of the train = 72 km/ hr

[It means that the train travels 72 km in 1 hour]

Now,

72 km/ hr = 72 × 1000 m / 3600 s = 20 m/s

{ 1 km = 1000 m and 1 hr = 3600 min }

Hence,

It will pass 80 metre long tunnel in :-

80/20 s = 4 seconds

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Answer 2

Step-by-step explanation:

speed of train in m/sec is 74× 1000/3600=20m/s

now time is 12 sec

d=t×s,. 12×20= 240m

now length of train is 240 m

while crossing a tunnel of 80 m long total distance will be 240+80= 320m

now time for crossing tunnel will be ,T=distance/speed

320/20 =16 sec