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 19 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
Deepak said:
1 decade ago
@niveditha
Since both train crossing each other in 23s, so have to multiply 23 by sum of speed of both train.
Since both train crossing each other in 23s, so have to multiply 23 by sum of speed of both train.
Shree said:
1 decade ago
Its simple .
T = D/S
Therefore total distance = 27x+17y and total speed = x+y
Total time = 23
23= 27x+17y/x+y
T = D/S
Therefore total distance = 27x+17y and total speed = x+y
Total time = 23
23= 27x+17y/x+y
Jyotirmoy said:
1 decade ago
Let the speed of the two trains be a=x m/sec and b=y m/sec
Length of a=27x and b=17y
So (27x+17y)=23(x+y).
So 4x=6y
So x/y=3/2
[In First sight I thought as the 1st train is taking more time to cross the man , so it will be the slower train, but as the lenght of the 1st train longer so it has taken longer time althought it is the faster train]
Length of a=27x and b=17y
So (27x+17y)=23(x+y).
So 4x=6y
So x/y=3/2
[In First sight I thought as the 1st train is taking more time to cross the man , so it will be the slower train, but as the lenght of the 1st train longer so it has taken longer time althought it is the faster train]
Rajkumar said:
1 decade ago
Let the speed of the two trains be a=x m/sec and b=y m/sec,
crossing time=23sec
formula :distance=speed*time
for 1st train,distance,u=x*27=27x
for 2nd train,distance,v=y*17=17x
suppose in opposite direction the formula is time=u+v/a+b
therefore,27x+17x/x+y=23
27x+17y=23(x+y)
27x+17y=23x+23y
27x-23x=23y-17y
4x=6y
x/y=6/4
x/y=3/2
x:y=3:2
crossing time=23sec
formula :distance=speed*time
for 1st train,distance,u=x*27=27x
for 2nd train,distance,v=y*17=17x
suppose in opposite direction the formula is time=u+v/a+b
therefore,27x+17x/x+y=23
27x+17y=23(x+y)
27x+17y=23x+23y
27x-23x=23y-17y
4x=6y
x/y=6/4
x/y=3/2
x:y=3:2
Sachin kamble said:
1 decade ago
According to my opinion the first train crosses the man after crossing the other train i.e. 4 sec late and second train will crosses the man 6 sec earliar before it cross the other train .
Just take the ratio of 6:4 we get 3:2 i.e speed of seocnd train:speed of first train.
Just take the ratio of 6:4 we get 3:2 i.e speed of seocnd train:speed of first train.
Swetha said:
1 decade ago
It can also be solved like this using the methods of allegation and mixture 27 17.
23.
6 4.
Thus ratio is 6:4 3:2.
23.
6 4.
Thus ratio is 6:4 3:2.
Dhiraj said:
1 decade ago
(la+lb)/(Sa+Sb)=23
la/sa=27
la/sb=17
sa/sb=?
sa/sb=3:2
la/sa=27
la/sb=17
sa/sb=?
sa/sb=3:2
Nisha said:
1 decade ago
Hi friends .....
1 km =1000m
1 hr=3600s
So, km/hr = 1000/3600 = 5/18
It's clear.
1 km =1000m
1 hr=3600s
So, km/hr = 1000/3600 = 5/18
It's clear.
BhargaV said:
1 decade ago
Why km/hr to m/sec conversion takes 5/18 ???
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