Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 14)
14.
Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is:
Answer: Option
Explanation:
| Relative speed = (60 + 40) km/hr = |  |
100 x | 5 |  m/sec |
= | |
250 | m/sec. |
| 18 | 9 |
Distance covered in crossing each other = (140 + 160) m = 300 m.
| Required time = | |
300 x | 9 | sec |
= | 54 | sec = 10.8 sec. |
| 250 | 5 |
Discussion:
43 comments Page 4 of 5.
Gourish said:
1 decade ago
I have one confusion regarding the length as the trains are moving opposite direction the length should be the longest train time as the time taken to cross will be dependent on direction.
Had it been same direction the trains length should be added.
A ---------
--------------- B
Anyone please?
Had it been same direction the trains length should be added.
A ---------
--------------- B
Anyone please?
Vineet Nair said:
1 decade ago
I still don't understand as how we got 5/18?
Rajesh said:
1 decade ago
Me too still don't understand as how we got 5/18?
Any one can clarify.
Any one can clarify.
Nisha said:
2 decades ago
Why 9/250?
Harish said:
1 decade ago
1 km= 1000 m.
1 hr = 3600 sec.
So km/hr= 1000/3600= 10/36 = 5/18.
1 hr = 3600 sec.
So km/hr= 1000/3600= 10/36 = 5/18.
Vinayak said:
1 decade ago
A _______|
|_______________ B
Hence, Length = A+B.
As they start crossing each other when engine meet and end crossing when their tail meets.
Suman said:
1 decade ago
Hey we can cut it 250/9 = 125/3 we can write.
Rahul kumat said:
1 decade ago
How relative speed added? As in question number 9 also when trains moving in opposite direction relative is added in both case relative speed is added? How?
Ajit said:
1 decade ago
By using formula,
t = a+b/u+v, (train running opposite direction).
= (140+160) m/(40+60) km/hr = 300 m/250/9 m/s.
Now, t = 10.8 s.
t = a+b/u+v, (train running opposite direction).
= (140+160) m/(40+60) km/hr = 300 m/250/9 m/s.
Now, t = 10.8 s.
Rupa said:
1 decade ago
If it comes to opposite direction distance is subtracted. Why it is added here?
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers