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.
Saurabh said:
9 years ago
I couldn't get this part:
27x + 17y/x + y = 23.
As both trains are moving in opposite directions the equation must be:
27x + 17y/x - y = 23.
That is speeds must get subtracted why add both of them?
27x + 17y/x + y = 23.
As both trains are moving in opposite directions the equation must be:
27x + 17y/x - y = 23.
That is speeds must get subtracted why add both of them?
Sunil said:
10 years ago
Hi @Gokulakisan sorry to say 27+23 = 50 not for 60.
Gokulakisan S said:
10 years ago
You can use this simple method:
Time to cross men = tm.
Time to cross each other = te.
So 27(tm)+23(te) = 60.
17(tm)+23(te) = 40.
Then 60/40 = 3/2.
Therefore ratio is 3:2.
Time to cross men = tm.
Time to cross each other = te.
So 27(tm)+23(te) = 60.
17(tm)+23(te) = 40.
Then 60/40 = 3/2.
Therefore ratio is 3:2.
Anvesh Annu said:
10 years ago
There is a simple method to solve this problem.
##Cross method##:
27 17
\ /
\ /
23
/ \
/ \
6 4
i.e, 27-23 = 4.
23-17 = 6.
6:4 so it is 3:2.
##Cross method##:
27 17
\ /
\ /
23
/ \
/ \
6 4
i.e, 27-23 = 4.
23-17 = 6.
6:4 so it is 3:2.
Sandeep said:
10 years ago
It is simplest form. I'm happy.
Sikandar said:
10 years ago
Two train of length a meter and b meter are moving in opposite direction at you m/s and we m/s then time taken by the faster train to cross the slower train = a+b/u+v.
Or in same direction = a+b/u-v.
In above problem train are in opposite direction.
So a = 27x & b = 17y (x = speed of fastest train y = speed of slow train).
= 27x+17y/x+y = 23.
4x = 6y.
x:y = 3:2.
Or in same direction = a+b/u-v.
In above problem train are in opposite direction.
So a = 27x & b = 17y (x = speed of fastest train y = speed of slow train).
= 27x+17y/x+y = 23.
4x = 6y.
x:y = 3:2.
Abhijith said:
10 years ago
One of the similar way to improve our aptitude knowledge.
Sumitra said:
1 decade ago
Here the time taken by two trains itself 27 & 17 sec rt.
So we know the formula that speed=d/t. Let us take the speed of the two trains is x & y.
Then the corresponding distances are 27x and 17y.
Then t=d/s as per formula.
Time taken to cross each other is 23 sec.
Equate that time as 23 sec and to cross that man by both trains.
i.e (27x+17y)/(x+y) = 23.
Then solve the equation we will get the answer.
So we know the formula that speed=d/t. Let us take the speed of the two trains is x & y.
Then the corresponding distances are 27x and 17y.
Then t=d/s as per formula.
Time taken to cross each other is 23 sec.
Equate that time as 23 sec and to cross that man by both trains.
i.e (27x+17y)/(x+y) = 23.
Then solve the equation we will get the answer.
Rashmi said:
1 decade ago
Why is time considered as a distance or length. As per the question it is 27 seconds and 17 seconds? I see through out the discussion we consider seconds in meters. Could anyone clear my doubt please?
Vincent said:
1 decade ago
Let the speeds of the two trains be x m/sec and why m/sec respectively.
Reference to man standing on the platform.
Length of the first train = 27X metres,
Length of the second train = 17Y metres.
Total speed of train when crossing opposite direction is (x+y) m/s.
Two trains are crossing each other in 23 seconds.
So length of two trains using this condition is (x+y) 23 m.
So 27X+17Y = 23X+23Y.
4X = 6Y.
X/Y = 3/2.
Reference to man standing on the platform.
Length of the first train = 27X metres,
Length of the second train = 17Y metres.
Total speed of train when crossing opposite direction is (x+y) m/s.
Two trains are crossing each other in 23 seconds.
So length of two trains using this condition is (x+y) 23 m.
So 27X+17Y = 23X+23Y.
4X = 6Y.
X/Y = 3/2.
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