Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 9)
9.
Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:
Answer: Option
Explanation:
Relative speed = (60+ 90) km/hr
| = |  |
150 x | 5 |  m/sec |
| 18 |
| = | |
125 | m/sec. |
| 3 |
Distance covered = (1.10 + 0.9) km = 2 km = 2000 m.
| Required time = | |
2000 x | 3 | sec = 48 sec. |
| 125 |
Discussion:
107 comments Page 2 of 11.
Shalinwilson said:
7 years ago
No need to convert to m/s.
Because everything in m and h.
Simply relative speed = 60+90 = 150 km/h.
Distance = 1.1+9 = 2 km.
2/150 = .013 hr (in seconds its .013*60 *60 = 48 seconds.
Because everything in m and h.
Simply relative speed = 60+90 = 150 km/h.
Distance = 1.1+9 = 2 km.
2/150 = .013 hr (in seconds its .013*60 *60 = 48 seconds.
(2)
Madhav Kulkarni said:
6 years ago
Relative Speed in Opposite Direction = 60+50 = 150km/h=150*(5/18)=41.66.
Train Length = 1.10+0.9=2Km=2000.
Time=Distance/Speed=2000/41.66=48.
So, the Answer is 48.
Train Length = 1.10+0.9=2Km=2000.
Time=Distance/Speed=2000/41.66=48.
So, the Answer is 48.
(2)
Jinni said:
5 years ago
The time for the long train will be the same right?
(2)
Mohd. Nafees said:
2 decades ago
Hi, can you pleas explain me that why you multiply 2000 with 3/125. Why it is not multiply by 125/3?
(1)
Gaurav said:
1 decade ago
@Jyoti:
When slower train will cross the faster train, it means both train has crossed each other , so don't get confused with that.
The question is simply asking when both train will cross each other.For that total distance will be the sum of the lengths of both trains. And total(relative) speed also will be the sum of speeds of both the trains.
When slower train will cross the faster train, it means both train has crossed each other , so don't get confused with that.
The question is simply asking when both train will cross each other.For that total distance will be the sum of the lengths of both trains. And total(relative) speed also will be the sum of speeds of both the trains.
(1)
Snape said:
1 decade ago
Can anyone explain why we are taking 2km as the distance ?
"The time taken by the slower train to cross the faster train" means the time taken by the tip of the slower train's engine to travel from faster train's engine to faster train's end ... right ??
So ideally the distance should be .9km (length of faster train). However the speed will remain 150 kmph.
"The time taken by the slower train to cross the faster train" means the time taken by the tip of the slower train's engine to travel from faster train's engine to faster train's end ... right ??
So ideally the distance should be .9km (length of faster train). However the speed will remain 150 kmph.
(1)
Dharmender said:
1 decade ago
@Sekhar.
If Initially you are not convert distance and speed in meter and m/s then after getting time you multiply only by 3600 for getting 48 sec.
Because Unit of Time is Only hour or seconds.
As T=D/S
So unit of T=(Unit of distance)/(Unit of Speed)
So you get Unit of Time is Only hour or seconds
Time T=D/S = 2/150=1/75*3600=48 sec.
If Initially you are not convert distance and speed in meter and m/s then after getting time you multiply only by 3600 for getting 48 sec.
Because Unit of Time is Only hour or seconds.
As T=D/S
So unit of T=(Unit of distance)/(Unit of Speed)
So you get Unit of Time is Only hour or seconds
Time T=D/S = 2/150=1/75*3600=48 sec.
(1)
Adm said:
10 years ago
You have to add the lengths when you consider crossing each other and add speeds. For more understanding consider two trains moving at different speed and plot a graph for each sec as how much they cross each other and you will discover why the formula is:
Time for crossing = (Sum of length of two train)/(Sum of speed of two trains).
Time for crossing = (Sum of length of two train)/(Sum of speed of two trains).
(1)
Mainul Bangladesh Khilkhet said:
8 years ago
@Vijju.
You are right that we have to consider the faster train's length. But you have to keep concern about that both trains starts from opposite direction. So, both trains cross each others at the same time. So, when they cross each others from the opposite direction; so in that case individual length is not important. But total length of the trains is important to measure the total distance/way what they cross each others.
You are right that we have to consider the faster train's length. But you have to keep concern about that both trains starts from opposite direction. So, both trains cross each others at the same time. So, when they cross each others from the opposite direction; so in that case individual length is not important. But total length of the trains is important to measure the total distance/way what they cross each others.
(1)
Sarang said:
7 years ago
Distance =speed*time,
1.10+.9=60+90*time,
2km=150km/h*time,
2000=150*5/18*time,
2000=750/18*time,
2000=41.66*time,
2000/41.66=time,
Time=48 s.
1.10+.9=60+90*time,
2km=150km/h*time,
2000=150*5/18*time,
2000=750/18*time,
2000=41.66*time,
2000/41.66=time,
Time=48 s.
(1)
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