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:
282 comments Page 27 of 29.
Vivek said:
2 decades ago
speed:- 54*5/18= 15 m/sec
length of the train:-15*20= 300 m.(distance= speed * time)
length of the platform:-x
Speed = Distance /Time
15=300+x/36
300+x=540
x=540-300
x=240
length of the train:-15*20= 300 m.(distance= speed * time)
length of the platform:-x
Speed = Distance /Time
15=300+x/36
300+x=540
x=540-300
x=240
Shelly said:
2 decades ago
Thanks Rahul.
Karthik said:
2 decades ago
Shortcut:
Minus the both time of the train to cross the platform as well as man (reference point).
T = 36 sec, t = 20 sec.
T - t = 16 sec.
With the normal formula Length = Speed * Time
(i.e) 15 m/s * 16 sec = 240 metres.
Minus the both time of the train to cross the platform as well as man (reference point).
T = 36 sec, t = 20 sec.
T - t = 16 sec.
With the normal formula Length = Speed * Time
(i.e) 15 m/s * 16 sec = 240 metres.
Magesh said:
2 decades ago
Guys listen.
Take a point as man standing on the platform. So the moving train pass the point at the time of 20 sec.
So, Length of the train = (15 x 20)m = 300 m.
Take a point as man standing on the platform. So the moving train pass the point at the time of 20 sec.
So, Length of the train = (15 x 20)m = 300 m.
Gaurang said:
2 decades ago
Amit thanks for answer correctly.
Remy said:
2 decades ago
How come (300+x) /15?its not said the man stands at the beginning of platform. If hes somwhere in the middle how come we add the length of the train 300 m ?
Nagashree said:
2 decades ago
Here man is standing in the platform, and we have to calculate the length of platform.
Hence we hav to multiply by 20 & not by36. Man in platform is reference point to us.
Hence we hav to multiply by 20 & not by36. Man in platform is reference point to us.
Frank said:
2 decades ago
Whenever u get two timings subtract the highest from the lowest.
Eg: 36 - 20 = 16
16*15 (after converting it to m/sec) = 240.
Eg: 36 - 20 = 16
16*15 (after converting it to m/sec) = 240.
Amit Kr. Soni said:
2 decades ago
Finally I solve question in my own language.
Time to cross the man = 20 sec
Speed of train = 54 km/hr, = 54*5/18, 15 m/sec .......... (1)
Now length of train = 20*15 (fm distns = spd * time) = 300 mtr
Now let length (ditns) of pltfrm = x mtr.
Totl lenth (distns) = 300 + x
Spd = 15 m/sec ........from eqan(1)
According to question,
300 + x/15 = 36, [b'coz trn complet d totl distns in 36 sec]
So x = 540 - 300 = 240 Answer
Time to cross the man = 20 sec
Speed of train = 54 km/hr, = 54*5/18, 15 m/sec .......... (1)
Now length of train = 20*15 (fm distns = spd * time) = 300 mtr
Now let length (ditns) of pltfrm = x mtr.
Totl lenth (distns) = 300 + x
Spd = 15 m/sec ........from eqan(1)
According to question,
300 + x/15 = 36, [b'coz trn complet d totl distns in 36 sec]
So x = 540 - 300 = 240 Answer
Rahul said:
2 decades ago
Length of the train is always calculated considering the train passes through a REFERENCE POINT. Here platform cannot be a REFERENCE POINT as it has some length. Thus man is taken as REFERENCE POINT to calculate the length of the train. Here train takes 20 seconds to cross REFERENCE POINT (man). Thus the train speed is multiplied by 20 seconds (15*20) to calculate the length of the train.
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