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 1 of 4.
Udaya said:
5 years ago
According to me;
300m long train cross-platform in 39 sec.
Cross pole in 18 sec (39-18= 21sec).
(Cross-Platform means platform +train)
(Cross Pole means only train length).
Extra time it takes 21 sec.
"18 sec ------ 300m.
21sec -------???? M.
21/18 * 300 = 350m.
300m long train cross-platform in 39 sec.
Cross pole in 18 sec (39-18= 21sec).
(Cross-Platform means platform +train)
(Cross Pole means only train length).
Extra time it takes 21 sec.
"18 sec ------ 300m.
21sec -------???? M.
21/18 * 300 = 350m.
(26)
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)
Bibek Nandy said:
2 years ago
300/18 = 50/3.
50/3x39 = 50x13 = 650.
650-300 = 350.
50/3x39 = 50x13 = 650.
650-300 = 350.
(6)
Kushi said:
4 years ago
Did anyone please explain it clearly?
(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)
Akash said:
5 years ago
50/3 * 21.
21*50 = 1050,
1050/3 = 350.
21*50 = 1050,
1050/3 = 350.
(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)
Hadhik said:
5 years ago
I am not getting. Please explain.
(1)
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)
Hemanth said:
7 years ago
In this problem, speed is not given then how to take 300/18?
(1)
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