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:
475 comments Page 30 of 48.
Venkatesh said:
8 years ago
Thank you @Nagapriya.
Ganga said:
8 years ago
Why we subtract (x-5)?
Shailesh Hiremath said:
8 years ago
So, kilometre & minutes will be calculated as 1 km=1000 mtrs and 60 minutes =3600 seconds.
If you divide 3600/1000 = 5/18.
If you divide 3600/1000 = 5/18.
Sunil said:
8 years ago
Thank you all for the given explanations.
Basava g said:
8 years ago
First, we find total length to across moving man=125+((5*10^3)÷(3600))*10.
= 125+13.888.
= 138.88m.
The speed of train = total/time.
= 138/10,
= 13.88m/s.
This one convert into km/hrs.
= 13.88 * 3600,
= 50km/hrs.
= 125+13.888.
= 138.88m.
The speed of train = total/time.
= 138/10,
= 13.88m/s.
This one convert into km/hrs.
= 13.88 * 3600,
= 50km/hrs.
Manjunath said:
8 years ago
Hi, anyone please explain to me why we should take 5/18?
Rachit said:
8 years ago
RELATIVE SPEED OF TRAIN WITH RESPECT TO MAN RUNNING= (x-5)km/hr.
TIME=DISTANCE/RELATIVE SPEED.
Therefore we know that- to convert km/hr to m/s we have to use,
(x-5) * 5/18)m/sec.
TIME=DISTANCE/RELATIVE SPEED
10=125/(x-5)*5/18.
10=TIME,125=DISTANCE,(x-5)*5/18=RELATIVE SPEED
CALCULATION-
10=125/(x-5)*5/18,
10=125*18/5x-25,
10=2250/5x-25,
10(5x-25)=2250,
50x-250=2250,
50x=2500,
x=50km/hr.
TIME=DISTANCE/RELATIVE SPEED.
Therefore we know that- to convert km/hr to m/s we have to use,
(x-5) * 5/18)m/sec.
TIME=DISTANCE/RELATIVE SPEED
10=125/(x-5)*5/18.
10=TIME,125=DISTANCE,(x-5)*5/18=RELATIVE SPEED
CALCULATION-
10=125/(x-5)*5/18,
10=125*18/5x-25,
10=2250/5x-25,
10(5x-25)=2250,
50x-250=2250,
50x=2500,
x=50km/hr.
Ananya said:
8 years ago
How can the answer be 50 that's the point x-5 would be 40 kmph?
Then how can b be the answer?
Then how can b be the answer?
Gaurav said:
8 years ago
Hey someone tell me, please. Why are you using 18/5 then 5/18?
Because the unit is m/s = 5/18 and you are using 18/5 in this problem.
Because the unit is m/s = 5/18 and you are using 18/5 in this problem.
Saikat Dey said:
8 years ago
Thanks to all for such nice explanations.
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