Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 18)
18.
A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform?
Answer: Option
Explanation:
| Speed = |  |
300 |  |
m/sec = | 50 | m/sec. |
| 18 | 3 |
Let the length of the platform be x metres.
| Then, | |
x + 300 | |
= | 50 |
| 39 | 3 |
3(x + 300) = 1950
x = 350 m.
Discussion:
39 comments Page 3 of 4.
Masud said:
8 years ago
@Koushik Roy.
300/18 m/s, it's the speed of train.
300/18 m/s, it's the speed of train.
Nikita said:
8 years ago
Thank you @Umesh.
Chakri said:
8 years ago
The speed to cross the pole and the platform is same there is no change in speed but why we have to take 18 sec?
Amrendra mishra said:
8 years ago
Let, Length of platform being static will be-(300+x).
and, the speed of train while passing pole is -300/18=150/9.
Hence;-
150/9=(300+x)/39,
x=350 ans.
and, the speed of train while passing pole is -300/18=150/9.
Hence;-
150/9=(300+x)/39,
x=350 ans.
Archana said:
8 years ago
How it's 350? I didn't understand please tell me the answer.
Abhi said:
7 years ago
@Sundar.
Thanks For the explanation.
Thanks For the explanation.
Hemanth said:
7 years ago
In this problem, speed is not given then how to take 300/18?
(1)
VENU said:
7 years ago
Speed = distance/time.
so i.e 300/18 =50/3.
Let distance of pltfrm is X.
so time taken by the trn to cross platform =(X+300)/50/3 =39,
i.e X+300=(39*50)/3,
650-300=X,
X=350.
so i.e 300/18 =50/3.
Let distance of pltfrm is X.
so time taken by the trn to cross platform =(X+300)/50/3 =39,
i.e X+300=(39*50)/3,
650-300=X,
X=350.
(2)
Akhila said:
7 years ago
A simple and Understandable explanation, Thanks. @Sundar.
Abhi said:
6 years ago
I think there are two kind of speeds are involved there. One is the speed by which it crosses the pole, second is the speed by which it crosses the platform. Once we calculate the speed Vp of train by which it crosses the platform (300/39 m/s), signal crossing speed Vs (300/18 m/s).
V = Vs-Vp = 8.97 m/s.
t = 39s.
S = 350meter is the answer.
V = Vs-Vp = 8.97 m/s.
t = 39s.
S = 350meter is the answer.
(1)
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