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:
42 comments Page 3 of 5.
Praveen Sharma said:
10 years ago
x = (300*9)/250.
x = 2700/250 {Cut zero by zero}
x = 270/25.
x = 54/5 {Both no. divided by 5}
x = 10.8 sec.
x = 2700/250 {Cut zero by zero}
x = 270/25.
x = 54/5 {Both no. divided by 5}
x = 10.8 sec.
Praveen said:
10 years ago
Let time is x sec. According to question:
Speed = Length/Time.
Both are in opposite so we add the speed if in same direction then sub speed.
So speed = 60+40 = 100 km/h.
We convert it in m/s by multiply 5/18.
So speed = 250/9 m/s.
Length = 140 m + 160 m = 300 m.
And time = x sec.
So 250/9 = 300/x.
So x = (300*9)/250.
And time = 10.8 sec.
Speed = Length/Time.
Both are in opposite so we add the speed if in same direction then sub speed.
So speed = 60+40 = 100 km/h.
We convert it in m/s by multiply 5/18.
So speed = 250/9 m/s.
Length = 140 m + 160 m = 300 m.
And time = x sec.
So 250/9 = 300/x.
So x = (300*9)/250.
And time = 10.8 sec.
Lokesh said:
10 years ago
How can come 54/5 = 10.8?
Kavitha said:
10 years ago
Its good thank you so much my child is learn now she is clever.
Rupa said:
1 decade ago
If it comes to opposite direction distance is subtracted. Why it is added here?
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.
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?
Suman said:
1 decade ago
Hey we can cut it 250/9 = 125/3 we can write.
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.
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.
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