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 6 of 24.
GUFRAN said:
1 decade ago
Let, the ist train speed v1=X m/s and T1=27s
2nd trin speed V2=Y m/s and T2=17s
Then S1=V1*T1=27x
S2=V2*T2=17Y
Both are in opposite dir. Then speed is S=S1-S2=27X-17Y
They cross each other means time difference 23(X-Y)=23X-23Y
now...
27X-17Y=23X-23Y
4X=-6Y
X/Y=-3/2=3/2(BECZ speed is not -ve)
X:Y=3:2
2nd trin speed V2=Y m/s and T2=17s
Then S1=V1*T1=27x
S2=V2*T2=17Y
Both are in opposite dir. Then speed is S=S1-S2=27X-17Y
They cross each other means time difference 23(X-Y)=23X-23Y
now...
27X-17Y=23X-23Y
4X=-6Y
X/Y=-3/2=3/2(BECZ speed is not -ve)
X:Y=3:2
Manish said:
7 years ago
27 and 17 are the length of the train and the speed of these train respectively x mtr/sec and y mtr/sec.
So 27x+17x are there relative speed of the train.
(27x+17y)/(x+y)=23.
Here 23 is given time in which the Cross each other's train after solving the above eq...
We get 4x=6y.
x/y=2/3 that's solved.
So 27x+17x are there relative speed of the train.
(27x+17y)/(x+y)=23.
Here 23 is given time in which the Cross each other's train after solving the above eq...
We get 4x=6y.
x/y=2/3 that's solved.
Dhinesh said:
2 years ago
Well, I have something different, 1st train is 27 sec so take this time as a total as 100% minus the 2nd train which is 17 sec so 62. 96 % is the percent of 1st train slower than the second train or vice versa.
So, 62.
96 is a 3 ratio to 100 so the remaining 38.04 is 2.
So, it's 3:2 am I right?
So, 62.
96 is a 3 ratio to 100 so the remaining 38.04 is 2.
So, it's 3:2 am I right?
(29)
Mobarak said:
1 decade ago
If two trains running at the speed x & y respectively in opposit direction then their relative velocity is (x+y) m/s.
Now if two trains cross each other then they have to cross total length of two trains which is (27x+17y).
Now time taken for crssng the total length = (27x+17y)/(x+y) i.e 23.
Now if two trains cross each other then they have to cross total length of two trains which is (27x+17y).
Now time taken for crssng the total length = (27x+17y)/(x+y) i.e 23.
Harry said:
9 years ago
I don't know its correct or not but I got the answer easily.
My step-- it's not telling about the speed so what we have here is 27 sec and 17 sec so its the ratio 27:17.
(27/9) = 3 : (17/9) =1.8 = 2.
So I got 3 : 2.
I don't know whether its right step or not, Please correct me, if it is wrong.
My step-- it's not telling about the speed so what we have here is 27 sec and 17 sec so its the ratio 27:17.
(27/9) = 3 : (17/9) =1.8 = 2.
So I got 3 : 2.
I don't know whether its right step or not, Please correct me, if it is wrong.
KD Phatak said:
1 decade ago
Let the speed of the two trains bee x and y meters.
Then a/c to the formula,
Speed = distance/time.
Distance = speed*time.
Distance of one train becomes 17x.
Second become 27y.
a/c to formula distance + distance/speed = time.
17x+27y/x+y = 23.
Now by solving you can get the answer.
Then a/c to the formula,
Speed = distance/time.
Distance = speed*time.
Distance of one train becomes 17x.
Second become 27y.
a/c to formula distance + distance/speed = time.
17x+27y/x+y = 23.
Now by solving you can get the answer.
Arunkumar said:
1 decade ago
Hi,
Nice explanation for why we need to.
1. Add the both trains speed which were running in opposite Directions with a reference point.
2. Subtract the both trains speed which were running in Same direction with a reference point.
http://en. Wikipedia. Org/wiki/Relative_velocity.
Nice explanation for why we need to.
1. Add the both trains speed which were running in opposite Directions with a reference point.
2. Subtract the both trains speed which were running in Same direction with a reference point.
http://en. Wikipedia. Org/wiki/Relative_velocity.
Priyesh verma said:
7 years ago
Two trains are moving in opposite direction with the speed of 36 k.m. /h and 54 k.m. /h cross each other in 12 seconds. The length of the 2nd train is half of the 1st train. The 1st train crosses a platform in 1. 30 minutes. Then what is the length of the platform? Please solve this.
Vidhyadhar said:
7 years ago
Let x=speed of train 1.
And y=speed of train 2.
Our task=x/y.
So, length of 1st train (d1)=x*27(dist=speed*time)
So, 2nd (d2) = y * 17.
Time taken by trains to cross each other =23 sec.
Time =dist/speed.
23=(d1+d2)/x+y.
23=(27*x+17*y)/x+y.
By solving this we get.
Result = x/y = 3/2
And y=speed of train 2.
Our task=x/y.
So, length of 1st train (d1)=x*27(dist=speed*time)
So, 2nd (d2) = y * 17.
Time taken by trains to cross each other =23 sec.
Time =dist/speed.
23=(d1+d2)/x+y.
23=(27*x+17*y)/x+y.
By solving this we get.
Result = x/y = 3/2
Shadab alam said:
1 year ago
@All.
If a train T1 takes 27 sec to cross the man which is more than the time taken by train T2 (17 sec) then how can the speed of Train T1 is greater than the speed of train T2?
option 2 is only correct when the length of train T1 is much greater than the length of train T2.
If a train T1 takes 27 sec to cross the man which is more than the time taken by train T2 (17 sec) then how can the speed of Train T1 is greater than the speed of train T2?
option 2 is only correct when the length of train T1 is much greater than the length of train T2.
(47)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers