Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 4)
4.
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:
Answer: Option
Explanation:
Let the speeds of the two trains be x m/sec and y m/sec respectively.
Then, length of the first train = 27x metres,
and length of the second train = 17y metres.
 |
27x + 17y | = 23 |
| x+ y |
27x + 17y = 23x + 23y
4x = 6y
| |
x | = | 3 | . |
| y | 2 |
Discussion:
233 comments Page 11 of 24.
Vinod reddy said:
9 years ago
Here is the formula when two trains crosses each other,
s1 + s2 = l1 + l2/time.
According to the problem.
x + y = (27x + 17y) /23.
27x + 17y = (x + y)23.
x/y = 3/2.
s1 + s2 = l1 + l2/time.
According to the problem.
x + y = (27x + 17y) /23.
27x + 17y = (x + y)23.
x/y = 3/2.
Hardik Mistry said:
1 decade ago
@Faty how can you say total speed is (x+y). Duh the train are moving in different direction. So their total speed need to be (x-y) according to your point of view.
Kumar said:
7 years ago
Distance = speed * time.
Time = 23 sec.
Time = total distance/speed,
Total distance = 27x+17y
The relative speed = x+y (opposite direction).
(27x+17y/x+y) = 23.
Time = 23 sec.
Time = total distance/speed,
Total distance = 27x+17y
The relative speed = x+y (opposite direction).
(27x+17y/x+y) = 23.
Nagendra said:
7 years ago
@Ganapathi, @Ashish Das,
The length of 1st Train is too long compared to 2nd Train. Hence even if though if it is faster, it took more time to cross the man.
The length of 1st Train is too long compared to 2nd Train. Hence even if though if it is faster, it took more time to cross the man.
Sumi said:
1 decade ago
hi nayana wen u cud understand till 4x=6y then wats complex there just bring y and 4 to the opp side then x/y=6/4
cancel by gcd thats it get the solution 3/2
cancel by gcd thats it get the solution 3/2
Manoj said:
5 years ago
How possible 3:2?
Because the first train takes more time than the second one. But the speed ratio is 3:2. Actually the second train moves fast than first.
Because the first train takes more time than the second one. But the speed ratio is 3:2. Actually the second train moves fast than first.
Ganapathi said:
7 years ago
Time taken by 1st train is more than the 2nd train then how speed ratio of 1st train is more than second train? I am not getting this. Please tell me.
Vivek Kumar said:
1 decade ago
Hey if we follow the physics concept then relative distance should decrease while crossing each other. Then it should be (27x - 17y)/(x+y). Isn't it?
Hima said:
8 years ago
Ratio of their speed = total distance travelled/total time taken= total speed.
(27x+17 y)/23 = (x+y),
27x+17y = 23x+23y,
4x = 6y,
x/y = 6/4,
3:2.
(27x+17 y)/23 = (x+y),
27x+17y = 23x+23y,
4x = 6y,
x/y = 6/4,
3:2.
Rahul said:
4 years ago
It's simple, speed is inversely proportional to time.
so 27-23 :23-17 {alligation rule}.
=6:4 (time ratio).
So the speed ratio will be 4:6 =2:3.
so 27-23 :23-17 {alligation rule}.
=6:4 (time ratio).
So the speed ratio will be 4:6 =2:3.
(50)
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