Aptitude - Problems on Trains - Discussion

Neetu's explanation s very nice.

Neetu your explanation cleared my doubt. Thanks.

Its not mentioned in ques that train passes pole and platform both. There is no need to add 240 with 650.

Neetus explanation is excelent.

@Kartikey Patel & Devanshu
First Me too Think like this
if
train 240 m long passes a pole in 24 seconds.
i.e 240 m : 24 sec
then 650 m : ? sec
650*24/240=65

and the ans is 65sec
....
After Saiyam Explanation i got clearly...
bfe netu he expn.
"so we include train length utill its last coach passing the platform.
time considered up to its last coach left the platform."
Thanks...

By the information given, can you find out the length of pole?plz inform me.

For problems on trains for most of the problems we use one formulae

time=(l1+l2)/s1+s2

for eg in the above problem

given length of train 240m and time 24 sec then speed=10m/sec

given length of platform 650

their is no speed s2 because platform is a stationary object

so substitue all the values in above formulae

we get time t=(240+650)/10= 89sec

Guys.. i can suggest u one thng that don't depend entirely on formulas, try

to analyze these type of problems logically..

coming to the prblm..

length of train = 240 mts

time taken to cross reference point(pole) = 24 sec

by the basic formula speed=length/time= (240/24) = 10 m/sec

they are asking the time taken by the train to cross the platform

imagine

------------------------- its a platform
650 m
______________ its train
240 m

train is said to be crossed the platform only if the entire train has pased over from it ryt... so clearly the total length that has to be travel to cross the platform is= (platform length + train length)

i.e. 650+240=890 m/sec

and again from the basic formula time= length/speed = 890/10 = 89 sec

If we are asked only the time taken to cover 650 m long platform, then the rigth answer is 65.

If we are asked to find the total time to cover the whole distance (240+650) , then the rigth answer is 89.

Can you tell me, why did we get 240 two times?

(Firstly 240/24, then after 240+650/10) So please explain me.