Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 25)
25.
A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is:
Answer: Option
Explanation:
Let the speed of the second train be x km/hr.
| Relative speed | = (x + 50) km/hr | |||||||
|
||||||||
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![]](/_files/images/aptitude/1-sym-cbracket-h1.gif)
Distance covered = (108 + 112) = 220 m.
 |
220 | = 6 | ||
|
250 + 5x = 660
x = 82 km/hr.
Discussion:
77 comments Page 4 of 8.
Apoorv said:
9 years ago
Sir, if the train is moving in an opposite direction the total distance one has to cover is the larger length. So why have we added the two?
Ravi said:
9 years ago
Simple solution method:.
Length of train 1st is = 108m.
Speed of train 1st is = 50km/h => 50 * 5/18 == 125/9 m/sec.
Length of trian - 2nd is = 112m.
Now, let the speed of 2nd tarin is = x m/sec.
Relative speed =x + (125/9).
Relative distance = 108 + 112 = 220 m.
Time = 6 sec.
Now, s = d/t.
=> x + 125/9 = 220/6 (therefore 220/6= 110/3).
=> x = (110/3) - (125/9).
=> x = 205/9 m/sec (205/9) * (18/5).
x = 82 km/h answer.
Length of train 1st is = 108m.
Speed of train 1st is = 50km/h => 50 * 5/18 == 125/9 m/sec.
Length of trian - 2nd is = 112m.
Now, let the speed of 2nd tarin is = x m/sec.
Relative speed =x + (125/9).
Relative distance = 108 + 112 = 220 m.
Time = 6 sec.
Now, s = d/t.
=> x + 125/9 = 220/6 (therefore 220/6= 110/3).
=> x = (110/3) - (125/9).
=> x = 205/9 m/sec (205/9) * (18/5).
x = 82 km/h answer.
Azam Khan said:
9 years ago
How Comes 5 in answer? I can't Understand please explain this.
Priyanka said:
9 years ago
Total distance = 112 + 120 = 220 m.
Time = 6 sec.
Relative speed = total distance / time,
=> 220/6 m/s
Speed in km/h,
=> 220/6 * 18/5 = 132.
Speed of second train = relative speed - speed of 1st train,
=> 132- 50 = 82 km/h.
Time = 6 sec.
Relative speed = total distance / time,
=> 220/6 m/s
Speed in km/h,
=> 220/6 * 18/5 = 132.
Speed of second train = relative speed - speed of 1st train,
=> 132- 50 = 82 km/h.
Rabvah said:
9 years ago
50*5/18 = 13.889 m/sec.
108 + 112/13.889 + x = 22.778.
Since it has to be in km/hr.
23.778*18/5 = 82 km/hr.
108 + 112/13.889 + x = 22.778.
Since it has to be in km/hr.
23.778*18/5 = 82 km/hr.
Moin said:
9 years ago
But can't do in direct formula of a + b/u + v = t? Then finding us there.
Rutika said:
10 years ago
S = D/T.
So, D = 108+112 = 220 m.
= 220/1000 km/hr.
T = 6 sec = 6/3600 = 1/600 hr.
S = 50 km/hr.
We assume second train speed 'x'.
Relative speed = 50 km/hr+x km/hr.
S = D/T.
= 50+x = 220/1000*600.
= 50+x = 22*6 = 50+x = 132.
x = 82 km/hr.
So, D = 108+112 = 220 m.
= 220/1000 km/hr.
T = 6 sec = 6/3600 = 1/600 hr.
S = 50 km/hr.
We assume second train speed 'x'.
Relative speed = 50 km/hr+x km/hr.
S = D/T.
= 50+x = 220/1000*600.
= 50+x = 22*6 = 50+x = 132.
x = 82 km/hr.
Sajan said:
10 years ago
Distance = (220/1000) km {Want to convert meter into kilometer).
Time = (6/3600) seconds {Second into hours - one hour has 3600 seconds}.
Distance/Time = Speed.
= (220/1000)/(6/3600) = x+50 km {Opposite speed should be added).
Now without converting, follow normally:
220/6*3600 = (50+x) speed (If goes 220 m within 6 seconds, what is the distance per hour or 3600 seconds).
132000 m per hour = (50+x).
So, 132 kilometer = (50+x).
x = 132-50 = 82.
Time = (6/3600) seconds {Second into hours - one hour has 3600 seconds}.
Distance/Time = Speed.
= (220/1000)/(6/3600) = x+50 km {Opposite speed should be added).
Now without converting, follow normally:
220/6*3600 = (50+x) speed (If goes 220 m within 6 seconds, what is the distance per hour or 3600 seconds).
132000 m per hour = (50+x).
So, 132 kilometer = (50+x).
x = 132-50 = 82.
Arun said:
10 years ago
Relative speed = x+50 km/hr.
6 = 220/(x+50)*(5/18).
5/3 = 220/(x+50).
x+50 = 132.
x = 82 m/sec.
Please explain, how km/hr.
And one more method.
6/3600= (220*10^-3)/(x+50).
x+50 = 600*0.22.
x = 142-50.
x = 92 km/hr.
Now I am totally confused. Please help.
6 = 220/(x+50)*(5/18).
5/3 = 220/(x+50).
x+50 = 132.
x = 82 m/sec.
Please explain, how km/hr.
And one more method.
6/3600= (220*10^-3)/(x+50).
x+50 = 600*0.22.
x = 142-50.
x = 92 km/hr.
Now I am totally confused. Please help.
(1)
Rishav kumar said:
10 years ago
Yes answer is correct but checking through reverse process.
Let x = 82 km/h and we have find time to cross each other. Then then the answer will come 6 sec. So it is correct.
Let x = 82 km/h and we have find time to cross each other. Then then the answer will come 6 sec. So it is correct.
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