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 2 of 4.
Kirtijyoti said:
5 years ago
D should be the answer. It is not given a train is moving at a uniform speed. So crossing the pole or platform the speed won't be uniform as per the question. So data is inadequate.
(2)
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)
Rishi said:
9 years ago
First, calculate a speed of the train.
Length = Speed * Time.
Then, S = L/T.
300/18 = 16.66 m/s.
Then, L = S * T.
(x + 300) = 16.66 * 39.
X = 350 m.
Length = Speed * Time.
Then, S = L/T.
300/18 = 16.66 m/s.
Then, L = S * T.
(x + 300) = 16.66 * 39.
X = 350 m.
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.
Manojsankar said:
1 year ago
@All.
Here, I am confused, why we take the speed of crossing the pole instead of crossing the speed of the platform? Anyone, please explain to me.
Here, I am confused, why we take the speed of crossing the pole instead of crossing the speed of the platform? Anyone, please explain to me.
(13)
Vinayaka N said:
10 years ago
Can anyone explain?
Why don't we add 39 seconds + 18 seconds as the train is travelling in the same direction as like in other previous problems?
Why don't we add 39 seconds + 18 seconds as the train is travelling in the same direction as like in other previous problems?
Ahaugis said:
1 decade ago
Question does not specify average speed or constant speed. Acceleration is required too answer the question correctly. That means [D] is correct.
Umesh said:
1 decade ago
Friends .
Shortcut:
speed =300/18=50/3m/sec
extra time taken to cross the platform=39-18=21
50/3*21=350m the length of platform
Shortcut:
speed =300/18=50/3m/sec
extra time taken to cross the platform=39-18=21
50/3*21=350m the length of platform
Waqas said:
1 decade ago
Hai dear sir, I am very confuse please help me explain that how we will measure the speed in detail with example?
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?
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