Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 27)
27.
A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:
Answer: Option
Explanation:
| 2 kmph = |  |
2 x | 5 |  |
m/sec = | 5 | m/sec. |
| 18 | 9 |
| 4 kmph = | |
4 x | 5 | |
m/sec = | 10 | m/sec. |
| 18 | 9 |
Let the length of the train be x metres and its speed by y m/sec.
| Then, |  |
x |  |
= 9 and | |
x | |
= 10. |
|
|
9y - 5 = x and 10(9y - 10) = 9x
9y - x = 5 and 90y - 9x = 100.
On solving, we get: x = 50.
Length of the train is 50 m.
Discussion:
106 comments Page 6 of 11.
Shilpa Rana said:
8 years ago
Thank @Mancy.
IDPRASAD said:
8 years ago
4-2=2 speed diff (same direction).
Kmph to mph.
2 * 5/18 = 5/9.
D=s * t
5/9 * 9 * 10 = 50.
Kmph to mph.
2 * 5/18 = 5/9.
D=s * t
5/9 * 9 * 10 = 50.
Naresh said:
8 years ago
The right answer is 50m. You will get the speed of the train is 22 kmph.So, Length is.
22-2 (velocity of first person) = length/9.
20*5/18 = length/9.
So, the length of the train is 50 m.
22-2 (velocity of first person) = length/9.
20*5/18 = length/9.
So, the length of the train is 50 m.
Sovaki said:
8 years ago
Can someone explain to me how you get (5/18)?
Dayana said:
8 years ago
Can anyone explain this x/y-5/9, why do use this?, which formulae did you applied, please explain.
Nikita said:
8 years ago
Thank you @Anagha.
Jugnu said:
8 years ago
Distance=(speed-5/9)*9 and distance=(speed-10/9)*10.
If distance is x then (speed-5/9)*9=(speed-10/9)*10.
Let speed be y.
(y-5/9) * 9 = (y-10/9) * 10.
9y-45 = 10y-100/9.
y = 305/9.
Then distance will be 300.
Am I right.
If distance is x then (speed-5/9)*9=(speed-10/9)*10.
Let speed be y.
(y-5/9) * 9 = (y-10/9) * 10.
9y-45 = 10y-100/9.
y = 305/9.
Then distance will be 300.
Am I right.
Shubham said:
9 years ago
How can we calculate the speed of the train in this?
Mojib Rahman said:
9 years ago
Let, Speed =X kmph.
Length = d km.
Again, relative speed Of A = x-2 & B=x-4.
9/3600 = d/x-2 (1).
10/3600 = d/x-4 (2).
We get, X=22.
From eq(1),
9/3600 = d/20.
d = 180/3600 = 1/20km = 1000/20m = 50m.
Length = d km.
Again, relative speed Of A = x-2 & B=x-4.
9/3600 = d/x-2 (1).
10/3600 = d/x-4 (2).
We get, X=22.
From eq(1),
9/3600 = d/20.
d = 180/3600 = 1/20km = 1000/20m = 50m.
Divya said:
9 years ago
Thank you @Anagha.
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