Aptitude - Problems on Trains - Discussion

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.

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.

Here, the Length of the train = (15 x 20)m = 300 m.

Length of the train = (15 x 20)m = 300 m.
how u took (15*20).

How you took (15*20)?

Guys I got the answer its because.

Distance=Time*Speed.

Distance= speed*time
300=15*20
this is length of a train only and we have to find out length of a plateform so we add length of both train and plateform becoz in case of bridge or plateform we can add both the length.
then
x+300/36=15
=240m

Me also have the same doubt.

Sahil,

Dis= s*t is okay.

Why didn't we take 300=15*36.

Please explain.

How is that you have taken (15 x 20) m as train length?