Question

A train 400m long is running at a speed 72 km/ HR . How much time does it to cross a telegraph post ??​

Answer 1

Answer:

distance=400m

speed=72×1000/3600

=2m/s

time=400/2

=200s

thus time taken the s 200 seconds

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Answer 2

Answer:

$\huge\sf{Solution}$

The length of train is given in metres . Hence, we shall convert it's speed in m/sec .

$\sf\red{Speed=72 \: Km/hr} \:$

$\sf\red{ = \frac{72 \times 1000}{3600} }$

$\sf\red{ = 20m/sec}$

$\sf\green{1km = 1000m} \\ \sf\green{1hr = 3600 \: sec}$

To cross a telegraph post , the train will cover a distance equal to its length , i.e 400 m . Let the required time = x sec.

Thus we have ,

Distance ( in m ) = 20 | 400

Time in ( sec ) = 1 | x

Clearly, it is a case of direct variation

$\sf\purple{ \frac{20}{1} = \frac{400}{x} }$

$\sf\purple{x = \frac{400}{20} = 20}$

◕ Hence time taken by the train to cross the telegraph posts is 20 seconds .

Step-by-step explanation:

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