Aptitude - Problems on Trains - Discussion

Here already taken by speed in 15m/sec.
And train length 15 × 20 = 300 m.
Then why take by the agin 15m/sec× 36 seconds can you explain this?

How 5/18 is came sir?

Answer 240m is possible only if the man is standing at the end of the station.

Am I right or wrong? Please anyone clarify.

The length of platform = x + 300/36 = 15 m/s.

Can someone explain why we write the 15 m/s on R.H.S of the equation?

I really could not understand. If someone knows then please help me.

I have solved this problem in a different way, is this the right way to solve it?

Speed=15 m/sec.
Total length of train is 300m,
let length of the plateform be x m,
total distance = speed * time,
x + 300 = 15*36,
x + 300 = 540,
x = 240m.

Why didn't we added the length of the man? Please explain.

Shortcut method:-

Train + Platform = 36 sec.
Train = 20sec.
Extra it takes 16 sec to travel platform.
Covert kmph to m/s because we need answer in m/ s.

54kmph*5/18 = 15m/s.
15* 20 = 300m train length.
It takes 20 sec ---> 300m
16sec ---> ?????
Less by more concept 16/20 *300 = 240 m.

Here, the length of the train is very small compared to real life.

Another easy method to solve this problem without using the variable x. Because if we use variable x for all the problems it will b bit confusing.

Solution is in question they asked about length so the formula is.

Distance = speed * time.

Since in question they had given speed in km/hr and the remaining terms are given in seconds added to that answer too given in meters.

Henceforth, its converted to m/sec.

So for converting it is been multiplied with 5/18.
Speed = 54 * (5/18).
= 15.

Since the train and the man in same direction it should be subtracted according to the rule.

So, time = (36-20).
= 16.

Now apply it in the formula.

Distance = speed * time.
= 15 * 16.
= 240.

Answer is 240.

Time taken to pass a station = 36s.
Time taken to pass a man = 20s.
Difference=16s.

We have,
Distance = Speed X Time.
= 15 X 16.
= 240m.