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:
494 comments Page 11 of 50.
Praveen said:
1 decade ago
Friends its a simple logic that if a men travel along the same direction of the train then the train speed is subtracted if it travel in opposite direction then train speed is added.
Hope you understand take this logic in your mind and solve any problem.
Hope you understand take this logic in your mind and solve any problem.
Samcena said:
1 decade ago
I made a relation like this (125m/v1-5*5/18) =10 sec. But the answer is not coming ? I converted 5 km/hr to m/s. Then I put it in above equation.
I put all the terms in m and sec (not in km and hour). My answer is coming to be 30. How is it? Help me out
I put all the terms in m and sec (not in km and hour). My answer is coming to be 30. How is it? Help me out
Sonu kumar from bihar said:
8 years ago
@Suraj Kumar
It is X-5=45,
So, X=45+5=50.
@Bouvthika.
45km/hr is the relative speed of train w.r.t. the man running speed, but we let the actual speed of the train is X km/hr, so actual speed of train- man running speed = relative speed of the train.
It is X-5=45,
So, X=45+5=50.
@Bouvthika.
45km/hr is the relative speed of train w.r.t. the man running speed, but we let the actual speed of the train is X km/hr, so actual speed of train- man running speed = relative speed of the train.
Jeevitha said:
9 years ago
Somebody asking that why x-5 here. Note that the man running in the same direction. So we have to subtract. If it is opp we have to add. Because man beats train spd. So man power should be subtracted. Then only we can get an exact speed of the train.
Ramu nayak said:
8 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).
Saggy said:
1 decade ago
Man is moving in same direction of train if man stop them train will less time to cross him but man is walking in same direction therefor man speed will be add in train speed if man walking in opposite direction of train then it minus from that.
Vishal Motwani said:
1 decade ago
Important points to remember:
The Relative speed when two movable things whose speeds x, y are moving in the same direction is = x - y.
The Relative speed when two movable things whose speeds x, y are moving in OPPOSITE direction is =x + y.
The Relative speed when two movable things whose speeds x, y are moving in the same direction is = x - y.
The Relative speed when two movable things whose speeds x, y are moving in OPPOSITE direction is =x + y.
Malik said:
1 decade ago
@Preethi.
Relative speed u-v = 80-62= 18km/hr=(18* 5/18)= 5 m/s.
Total length a+b = 110+130= 240 m.
Time to overtake = (a+b)/(u-v)[see formula 9 from formula section]
= 240/5
= 48 sec.
Am I correct?
Relative speed u-v = 80-62= 18km/hr=(18* 5/18)= 5 m/s.
Total length a+b = 110+130= 240 m.
Time to overtake = (a+b)/(u-v)[see formula 9 from formula section]
= 240/5
= 48 sec.
Am I correct?
Keerthana P Tawade said:
3 years ago
T = L/V1-V2
Where
T = time taken by train to pass the pole
L = Length of the train.
V1 = velocity of the train.
V2= Velocity of the man.
10 = 125/V1-5kmph.
v1-5kmph = 125/10*18/5 (converting m/s into km/h).
V1-5kmph = 45kmph,
V1 = 50kmph.
Where
T = time taken by train to pass the pole
L = Length of the train.
V1 = velocity of the train.
V2= Velocity of the man.
10 = 125/V1-5kmph.
v1-5kmph = 125/10*18/5 (converting m/s into km/h).
V1-5kmph = 45kmph,
V1 = 50kmph.
(108)
Rohit said:
1 decade ago
Why is the distance covered by man in 10 sec not considered? I believe the total distance would be the length of train + distance covered by man in 10 sec. Considering this the relative speed of train comes out to 55 km/hr. Please suggest.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers