Question

The ratio of the speed of two trains A and B running in the opposite direction is 5 : 15 . If each train is 200 m long and crosses each other in 10 s, then find the amount of time (in seconds) that train A takes to cross a man standing on a platform.

Answer 1

$\displaystyle\huge\red{\underline{\underline{Solution}}}$

Since The ratio of the speed of two trains A and B running in the opposite direction is 5 : 15

Let the speed of the two trains be

5x m/s and 15x m/s respectively

Since they are running in the opposite direction

So they travels in 1 sec = ( 5x + 15x ) = 20x m

Now each train is 200 m long and crosses each other in 10 s

So in order to cross each other they to cover a distance of ( 200 + 200) m = 400 m

So the required time to cross each other

$= \displaystyle \sf{ \frac{400}{20x} \: } \: \: sec$

$= \displaystyle \sf{ \frac{20}{x} \: } \: \: sec$

So according to the given condition

$\displaystyle \sf{ \frac{20}{x} \: } \: \: = 10$

$\implies \: \displaystyle \sf{ x = 2}$

So the speed of the train A is

$= \displaystyle \sf{5 \times 2 } \: \: \: m/s$

$= \displaystyle \sf{10 } \: \: \: m/s$

In order to cross a man sitting in the platform by the train A the train has to travel the length itself

So the required time is

$= \displaystyle \sf{ \frac{200}{10} } \: \: \:sec$

$= \displaystyle \sf{20 } \: \: \:sec$

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If a : b=c:d=e: f= 2:1 then (a + 2c + 3e) : (5b + 10d + 15f ) = ?

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Answer 2

Step-by-step explanation:

answer your question is .. 20