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.
Loki said:
3 months ago
@All.
Usually take 300+x and 300+y for platform and signal respectively but if we go by this there isn't enough data they have taken the pole as the stationery object as the beginning that is y it is so confusing they haven't mentioned something like that and did it.
Usually take 300+x and 300+y for platform and signal respectively but if we go by this there isn't enough data they have taken the pole as the stationery object as the beginning that is y it is so confusing they haven't mentioned something like that and did it.
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)
Santosh Kumar said:
2 years ago
Distance = 300m,
Time = 18.
Speed = Distance/Time.
= 300/18,
= 50/3.
Time = 18.
Speed = Distance/Time.
= 300/18,
= 50/3.
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)
Hadhik said:
5 years ago
I am not getting. Please explain.
(1)
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)
Akash said:
5 years ago
50/3 * 21.
21*50 = 1050,
1050/3 = 350.
21*50 = 1050,
1050/3 = 350.
(2)
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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