Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 26)
26.
Two trains are running at 40 km/hr and 20 km/hr respectively in the same direction. Fast train completely passes a man sitting in the slower train in 5 seconds. What is the length of the fast train?
Answer: Option
Explanation:
| Relative speed = (40 - 20) km/hr = |  |
20 x | 5 |  |
m/sec = | |
50 | |
m/sec. |
| 18 | 9 |
 Length of faster train = |
|
50 | x 5 | |
m = | 250 | m = 27 | 7 | m. |
| 9 | 9 | 9 |
Discussion:
72 comments Page 3 of 8.
Ujjwal said:
8 years ago
Use the concept of relative speed i.e. slower train is fixed and the faster train is moving with the speed of (40-20)km/hr=20km/hr. Then the men sitting in the slower train is also a stationary one wrt. faster train .then simply use the formula of a train moving with a velocity of 20 km/hr to pass a stationary object in 5 seconds.
MiniPanda said:
8 years ago
The relative speed b/w the train is 20kmph. It is easier to understand if you look in this way-- The faster train is moving at a speed of 20kmph and the slower train is 0kmph i.e. static. So now since the person sitting inside the train is also static we can simply treat this problem like "the time taken by a train to cross a pole" type.
GAURAV said:
8 years ago
How can we assume the man will be sitting on a forehead of the train? He can be sitting anywhere in the train.
I think the answer will be can't be determined until exact location of man is not mentioned.
I think the answer will be can't be determined until exact location of man is not mentioned.
Pardhu said:
8 years ago
Nice explanation, thank you all.
Manil Shylla said:
7 years ago
Please explain me with a simple step how we got 250/9?
Pratik Patil said:
7 years ago
Just consider that man is running at speed of 20 km/hr, then find the relative speed between train and man i.e. (40-20)km/hr=20km/hr=20*5/18 m/s=50/9 m/s.
The length of train (faster) = speed X time = 5*50/9 = 27 7/9 m.
The length of train (faster) = speed X time = 5*50/9 = 27 7/9 m.
Madhusudhan said:
7 years ago
How to simplify 250/9 to 27*7/9? Please explain clearly.
Kanishk jain said:
7 years ago
Actually, it means that the length of the faster train relative to the slower train.
That's why the answer is 250/9.
That's why the answer is 250/9.
Shashi said:
7 years ago
Rather than crossing man, if they asked the length of the slower train, then what will be the method?
Sumukh said:
6 years ago
Since the faster train is passing man sitting inside the slower train in 5 seconds. The length of slower train may be treated as man distance which is negligible just like pole. So, the right answer is C.
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