Aptitude - Problems on Trains - Discussion

Simple @Anil.

4x = 6y.
Then x/y = 6/4.

x/y = 3/2.

Therefore the ratio is 3:2.

Hi friends.

How to use mod method to calculate this problem?

Can any one say how does this length of the first and second trains are considered as 27x and 17y respectively?

It is very simple to understand the logic of 27x+17y/x+y=23 first we came across to know logic first of all we know the, speed=x/t in this way we assume that the sum of the two train lengths divided by assuming speeds is equal to relative crossing time is 23 seconds.

One of the question arise in your mind that is why we took length s of trains in sum because they cross each other with respect to man.

Thank you.

Dear friend cherry the logic is very simple to understand we know speed = distance/time in this way 27 is the time of one train to pass a man and "x"is the assuming speed I hope to you may be understand.

Also calculate as train 1 = 27sec.
Train 2 = 17sec.

Ratio of train 1 & train 2.

27/17 = 1.588.

We have an option 3/2 = 1.5.

Length = speed*time.

Means 27x+17y = (x+y)*23.

=>(27x+17x)/(x+y) = 23.

Let the speed of the two trains bee x and y meters.
Then a/c to the formula,

Speed = distance/time.
Distance = speed*time.

Distance of one train becomes 17x.
Second become 27y.

a/c to formula distance + distance/speed = time.
17x+27y/x+y = 23.

Now by solving you can get the answer.

There are 2 trains .
Here is some experiment ,one man is standing on platform.

Trian 1:
=========
we assume X is train 1 speed.
this train cross that man in 27X meters.

Trian 2:
===========
We assume Y is train 2 speed.
This train cross that man in 17Y meters.

We concentrate trains are moving in opposite direction.
So speed is X+Y.

Distance is (train_1_length+trian_2_length) = 27X+17Y.
Time = 23 seconds.

Formule : distance = speed*time.

27X+17Y = (X+Y)*23.

X/Y = 3/2.

Velocity = distance/time.
Let velocities are x, y m/s.

x = d1/27; y = d2/17;
d1 = 27x; d2 = 17y;

Step 2: According to relative speed, since they are running in opposite direction their speeds are added.

x+y = d1+d2/23.

Sub d1 and d2; find answer.