Question

speeds of two train ratio 3:4 .they are going in opposition direction along paraell tracks. if each takes 3 sec to cross a telegraph post.find time taken by train to cross each other completely​

Answer 1

Answer:

Here we will learn about the concept of two trains passes in the opposite direction.

When two train passes a moving object (having some length) in the opposite direction

Let length of faster train be l meters and length of slower train be m meters

Let the speed of faster train be x km/hr

Relative speed = (x + y) km/hr.

Then, time taken by the faster train to pass the slower train = (l + m) meters/(x + y) km/hr

Now we will learn to calculate when two trains running on parallel tracks (having some length) in the opposite direction.    

Step-by-step explanation:

Answer 2

$\huge\bf{Answer:-}$

3 seconds.

Further Explanation

Accoding to the given question:-

Let 3 be the speed of one train.

Let 4 be the speed of other train.

3 + 4 => 7 be the speed of both train.

3 second is the time of both trains to cross the telegraph.

Length of one train (3 × 3)=>9

Length of other train (4 × 3) = 12

(9 + 12) => 21 is the length of both trains when crossing the telegraph.

Using formula:-

Speed = Distance/Time

Time = Distance/Speed

Let T be the time.

$t = \frac{21}{7}$

Therefore the time taken is 3sec.