Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 4)
4.
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:
Answer: Option
Explanation:
Let the speeds of the two trains be x m/sec and y m/sec respectively.
Then, length of the first train = 27x metres,
and length of the second train = 17y metres.
 |
27x + 17y | = 23 |
| x+ y |
27x + 17y = 23x + 23y
4x = 6y
| |
x | = | 3 | . |
| y | 2 |
Discussion:
233 comments Page 13 of 24.
Naveen Kumar said:
1 decade ago
Hi I have one doubt.
How X and Y seconds become metres?
How X and Y seconds become metres?
Srinivasa raju said:
1 decade ago
Total Distance/Total Speed = Total Time;
27X+17Y/X+Y = 23.
27X+17Y/X+Y = 23.
Amit Jana said:
1 decade ago
#Krishna no this is not possible as you say. Then cross each other in 23 sec. Is have no sense?
Amit Jana said:
1 decade ago
#Vivek kumar.
Here the questions is : two train of length a and b are run in opposite directions at u m/sec. and v m/sec., then the time taken by the trains to cross each other = (a+b)/(u+v).
And if two train of length a and b are run in same directions at u m/sec. and v m/sec., then the time taken by the faster trains to cross the slower train = (a+b)/(u-v)
Here the questions is : two train of length a and b are run in opposite directions at u m/sec. and v m/sec., then the time taken by the trains to cross each other = (a+b)/(u+v).
And if two train of length a and b are run in same directions at u m/sec. and v m/sec., then the time taken by the faster trains to cross the slower train = (a+b)/(u-v)
Krishna said:
1 decade ago
If I divide speed of one train 27 divided by another its almost 1.5 can I choose 3:2. Is it a pure coincidence ?
Vadivel said:
1 decade ago
Why should both trains have different length. Even sometimes they can have same length and can run in different speeds right. Then how can we do like that. Can anyone explain please?
Vivek Kumar said:
1 decade ago
Hey if we follow the physics concept then relative distance should decrease while crossing each other. Then it should be (27x - 17y)/(x+y). Isn't it?
Sarath said:
1 decade ago
Lets assume,
The train 1 speed= x m/sec ==> distance traveled by the train 1= 27*x m.
Similarly assume the speed of the train 2 is y m/sec then the train 2 has traveled a distance of 17*y meter.
The total distance (x+y)*23 m.
Therefore,
23(x+y) = 27x+17y.
23x+23y=27x+17y.
==> 4x=6y.
==> x/y=3/2.
Therefore x:y= 3:2. Answer B.
The train 1 speed= x m/sec ==> distance traveled by the train 1= 27*x m.
Similarly assume the speed of the train 2 is y m/sec then the train 2 has traveled a distance of 17*y meter.
The total distance (x+y)*23 m.
Therefore,
23(x+y) = 27x+17y.
23x+23y=27x+17y.
==> 4x=6y.
==> x/y=3/2.
Therefore x:y= 3:2. Answer B.
Het said:
1 decade ago
@Arashan has describe very well with formula of speed.
SWETHA.T said:
1 decade ago
SPEED = DISTANCE/TIME.
DISTANCE/SPEED = TIME.
i.e 27X+17Y/X+Y = 23.
DISTANCE/SPEED = TIME.
i.e 27X+17Y/X+Y = 23.
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