Aptitude - Problems on Trains - Discussion

Please explain to sutract -5 but ans is 50.

How answer is 50 km/hr? Please explain to me.

So in the above problem let us consider that the speed of the person is 5 km\hr .

Leave the 5 as it is and then convert the km\hr into m\s
that means 1 km=1000m
and 60min=3600sec

Now when actually converted 3600\1000 that would give u the two zero gets cut and remains is 36\10 that would give u after dividing each by 2 i.e 18\5which means
(18m\5s)1.FRACTION

Now the major calculation,
Two object over here is Train and the Man consider them as A and B
where A is the Train as we have to find the speed of the train
then B is the speed of the Man is 5
so we get A-5

We had 125m the length of train time 10 seconds
already these are in meters and in seconds no need to convert them so 125m\10s u get (25m\2sec) 2.FRACTION

Now, finally get the first fraction and the second fraction together i.e (18\5)*(25\2)u get 45 as answer when u calculate
then A-5=45 ,when u move the negative -5 to this side of the equals too sign it converts to positive giving u A=45+5

i.e 50 so A=50 and A is the speed of train!!hope u'll understood!!take care!!

According to the question,

Trains length = 125m (distance).
Speed = 10sec,
Mans speed = 5km/hr.

The km the train hasn't travelled is not been given so take it as = X km/hr.
Man moves in the same direction = 5km/hr .

When two bodies are moving in the same direction then you will have to subtract it. If the person is moving on the opposite side he feels the train is moving faster hence u got to add But here it's on the same direction.

So, it's (x-5)km/hr.
When you want to convert kilometre into metres multiply with 5/18
So , (x-5) 5/18 ---> (1) i.e time

Time =distance/speed.
= 125/10 --> (2).

Therefore,
Time = distance/speed.
(X-5) 5/18 = 125/10,
(X-5)5/18 = 25/2,
(X-5) = 25/2 * 18/5 (simple cancellation).
(X-5) = 45,
X= 45+ 5,
X= 50.

length = speed * time = 5 * 10 = 50.

Solution:

Time = Distance/Speed.

Length of train=125m.

Speed of the person in the same direction is 5KM/hr i.e 25/18m/sec
the train takes 10 sec to cross i.e our time.

Let take x as the speed of the train.

So according to the above formula.
10 = 125/x-(25/18),
10 = 125 * 18/18x-25.
x = 13 * 18/5 m/sec.

To make it KM/hr we have to multiply it by the help of 18/5.
13*18/5 * 18/5 = 46km/hr.

So ans should be 46.

Thanks all for explaining it.

Why is it divided by 18/5?

Why 125/10 the 10 is divided 125 please explain it.

Hi friends,the problem is very simple.Think in this way.Assume that the man is not moving(standing like a pole),now findout the speed of the train using the data.
LENGTH OF THE TRAIN=125m.
TIME TAKEN BY THE TRAIN TO CROSS THE MAN(assume standing)=10sec
w k t velocity=distance(length of the train)/time.
v=(125/10)m/s
v=(25/2)m/s
convert m/s into km/hr
v=(25/2)* (3600/1000) or (25/2)*(18/5)
v=45 km/hr
45 km/hr is the train speed if the person is standig(not moving).
But in the problem person is moving and that to he is moving in the same direction in which train going,so that's y add the speed of the man to the speed of the train then we will got the correct answer.
speed of the train+speed of the man=45+5=50 km/hr.