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 5 of 8.
Vaishna.v said:
1 decade ago
I have cleared it in another way:
We have to calculate the length of faster train only.
The relative speed = (40-20) km/hr = 20 km/hr.
Let the length of the faster train be f.
Then, (f/20 km/hr) = 5.
20 km/hr = 20*5/18 s = 50/9 s.
(9f/50) = 5.
250/9 is the answer.
We have to calculate the length of faster train only.
The relative speed = (40-20) km/hr = 20 km/hr.
Let the length of the faster train be f.
Then, (f/20 km/hr) = 5.
20 km/hr = 20*5/18 s = 50/9 s.
(9f/50) = 5.
250/9 is the answer.
Grish said:
1 decade ago
The position of man is supposed to be ignore. It's a confusing element. Anyway the speed of slower train?
Divyansh said:
1 decade ago
When the question says this type that man is sitting but not tells the exact position the apply simple formula speed(Relative) = Distance/Time.
Ratnesh said:
1 decade ago
Hey to convert km/hr to m/s we have to use this conversion unit,
i.e 1000/(60*60)= 1000/3600.
Here 1 km = 1000 m and 1 hr = 60*60 =3600 seconds.
And when simplified it will give 5/18.
Hope your doubt about 18 would be clear now?
i.e 1000/(60*60)= 1000/3600.
Here 1 km = 1000 m and 1 hr = 60*60 =3600 seconds.
And when simplified it will give 5/18.
Hope your doubt about 18 would be clear now?
Alu said:
1 decade ago
What is that 18 denoting to in 5/18?
Sunny said:
1 decade ago
Here also the faster train crossing the slower train hence we get the length of 2 trains, not the faster train.
Sunny said:
1 decade ago
Please can anyone tell me the length of the slower train?
Bhavya said:
1 decade ago
Relative speed =40-20= 20 is okay after why we multiplied with 5/18, and wt is that 5/18?
Mancy said:
1 decade ago
Hi @Shweta.
We are taking relative speed because in the question direction of moving trains are mentioned so for calculating the length firstly we've to take relative speed.
We are taking relative speed because in the question direction of moving trains are mentioned so for calculating the length firstly we've to take relative speed.
Shwetha said:
1 decade ago
Hey can anyone tell me why we have to take relative speed. When question is regarding fast train length?
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