Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 5)
5.
A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform?
Answer: Option
Explanation:
| Speed = |  |
54 x | 5 |  m/sec = 15 m/sec. |
| 18 |
Length of the train = (15 x 20)m = 300 m.
Let the length of the platform be x metres.
| Then, | x + 300 | = 15 |
| 36 |
x + 300 = 540
x = 240 m.
Discussion:
276 comments Page 19 of 28.
Bhatu said:
1 decade ago
Friends I think the actual answer is 540m, please tell me anybody it is correct or not?
Sabira said:
1 decade ago
S = 54*(5/18) = 15m/s.
Total time=30-20 = 16.
Length = 15*16 = 240.
Total time=30-20 = 16.
Length = 15*16 = 240.
Sikkanthar said:
1 decade ago
Nice answers. Here they are using the formula is,
(train length + plat form length) / time = speed.
They are calculating the length of the train by using the given data.
Then substitute all the known values and finally got the result.
(train length + plat form length) / time = speed.
They are calculating the length of the train by using the given data.
Then substitute all the known values and finally got the result.
Udaya said:
1 decade ago
We can also do like this guyz.
Total time taken to cross the platform = 36-20 = 16.
Because the person is in the platform which the train crosses.
Now length= 15*16 = 240m.
Total time taken to cross the platform = 36-20 = 16.
Because the person is in the platform which the train crosses.
Now length= 15*16 = 240m.
Tina said:
1 decade ago
Total time = 36sec - 20sec = 16 sec.
Speed = 54*(5/18) = 15 m/sec.
Length = speed * time = 15 * 16 = 240m.
Speed = 54*(5/18) = 15 m/sec.
Length = speed * time = 15 * 16 = 240m.
Carlo said:
1 decade ago
Explanation is right.
Distance = time * speed.
Distance or length = 20 * 15 = 300m.
We can't take 36 * 15 because we already used 36 sec to get 540m
so to get the relative speed:
x + 300 = 540.
x = 240m.
Distance = time * speed.
Distance or length = 20 * 15 = 300m.
We can't take 36 * 15 because we already used 36 sec to get 540m
so to get the relative speed:
x + 300 = 540.
x = 240m.
Swayoni said:
1 decade ago
Why can't we take 15*36 to find the length of the train?
Jinita said:
1 decade ago
Why took 15*20? and the method (36-20) i.e. taking difference can be applicable?
Reshmi said:
1 decade ago
I have the same doubt & Its not clear from all these explanations. Why you took 15*20 as the distance value?
Amol said:
1 decade ago
Friends I think time req. To cross man (20) is less than time req. To cross station (36). So length of station is more than length of train.
So,
Total length of station = 20sec*15m/sec + 16sec*15m/sec.
= lth of train + remaining lth of platform.
For 16 sec,
= 300+240.
= 540m.
So,
Total length of station = 20sec*15m/sec + 16sec*15m/sec.
= lth of train + remaining lth of platform.
For 16 sec,
= 300+240.
= 540m.
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