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:
234 comments Page 13 of 24.
James said:
1 decade ago
Can someone please explain to me how 27x+17y = 23x + 23y & 4x + 6y?
Sharad said:
1 decade ago
@James.
27x+17y = 23x+23y.
27x-23x = 23y-17y.
4x = 6y.
4x/2 = 6y/2.
2x = 3y.
x/y = 3/2.
27x+17y = 23x+23y.
27x-23x = 23y-17y.
4x = 6y.
4x/2 = 6y/2.
2x = 3y.
x/y = 3/2.
Adi said:
1 decade ago
Short cut:
T2 = 23-17 = 6.
T1 = 27-23 = 4.
S1/S2 = T2/T1.
= 6/4 = 3/2.
T2 = 23-17 = 6.
T1 = 27-23 = 4.
S1/S2 = T2/T1.
= 6/4 = 3/2.
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.
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?
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.
Abhijith said:
10 years ago
One of the similar way to improve our aptitude knowledge.
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.
Sandeep said:
10 years ago
It is simplest form. I'm happy.
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.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers