Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 2)
2.
A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
Answer: Option
Explanation:
| Speed of the train relative to man = |  |
125 |  m/sec |
| 10 |
| = | |
25 | m/sec. |
| 2 |
| = | |
25 | x | 18 | km/hr |
| 2 | 5 |
= 45 km/hr.
Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.
x - 5 = 45 
x = 50 km/hr.
Discussion:
481 comments Page 12 of 49.
Lavanya said:
7 years ago
Why do we to subtract 45-5? please clarify that.
Hari kumar said:
7 years ago
50 is the right answer.
Chandan Azad said:
7 years ago
T(time required) = Lt(length of train) + Lo(length of object)/ Ut(speed of Train)+,-Uo(speed of object) .
("-" when train and object goes in same direction.
"+" when train and object goes in opposite direction.)
10=(125+0)/(Ut-5*5/18).
Ut=125/9.
Ut=(125/9)*(18/5).
Ut=50km/hr.
("-" when train and object goes in same direction.
"+" when train and object goes in opposite direction.)
10=(125+0)/(Ut-5*5/18).
Ut=125/9.
Ut=(125/9)*(18/5).
Ut=50km/hr.
Ramya said:
7 years ago
Can anyone Explain this problem to me? I didn't understand this.
Robi said:
7 years ago
@Omkar Tanpure.
What is the relative speed? And why 45 is called relative speed? Please explain me.
What is the relative speed? And why 45 is called relative speed? Please explain me.
Vipin said:
7 years ago
Hi, I am not getting this. Please anyone help me to get it.
Farheen said:
7 years ago
To convert km/hr to m/sec we multiply it with 5/18.
If we are converting m/sec to km/hr we multiply it 18/5.
If we are converting m/sec to km/hr we multiply it 18/5.
Dhivya said:
7 years ago
L(train) = (speed of train-speed of object) * time.
125m = (St-5)km/hr * 10s,
112.5 * 18/5 = st - 5,
St = 50km/hr.
125m = (St-5)km/hr * 10s,
112.5 * 18/5 = st - 5,
St = 50km/hr.
Akeer said:
7 years ago
@Ganesh.
The Relative means related to speed. The two trains are in which direction moving based on that we have to take the speed to add or sub.
The Relative means related to speed. The two trains are in which direction moving based on that we have to take the speed to add or sub.
Ramu nayak said:
7 years ago
Relative velocity is nothing but the velocity of body A to body B.
Case 1:
A and B moving in the same direction
Vr= Va-Vb. (Va>Vb)
Vr= Vb-Va (VB>Va)
Case 2:
A and B moving in opposite directions.
Vr=Va+VB. (Velocity not matters).
Case 1:
A and B moving in the same direction
Vr= Va-Vb. (Va>Vb)
Vr= Vb-Va (VB>Va)
Case 2:
A and B moving in opposite directions.
Vr=Va+VB. (Velocity not matters).
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