Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 27)
27.
A train overtakes two persons who are walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train is:
Answer: Option
Explanation:
| 2 kmph = |  |
2 x | 5 |  |
m/sec = | 5 | m/sec. |
| 18 | 9 |
| 4 kmph = | |
4 x | 5 | |
m/sec = | 10 | m/sec. |
| 18 | 9 |
Let the length of the train be x metres and its speed by y m/sec.
| Then, |  |
x |  |
= 9 and | |
x | |
= 10. |
|
|
9y - 5 = x and 10(9y - 10) = 9x
9y - x = 5 and 90y - 9x = 100.
On solving, we get: x = 50.
Length of the train is 50 m.
Discussion:
106 comments Page 10 of 11.
Ronie said:
7 years ago
@Mancy
Check your equation.
You wrote : 9y = 5+x.
y = 5+x/9. This is not possible you have divided x by 9 but haven't divided 5 by 9.
It would be y=5/9+ x/9.
Check your equation.
You wrote : 9y = 5+x.
y = 5+x/9. This is not possible you have divided x by 9 but haven't divided 5 by 9.
It would be y=5/9+ x/9.
Charan said:
7 years ago
Well said. Thanks all.
Divya Bisht said:
7 years ago
Can anyone tell me that why we take 2kmph nd 4kmph separate? Why we not done 4kmph+2kmph?
Meenu said:
7 years ago
Sir, how can you take 9y-5=x?
If we multiply by 9 all over the equation the that is 9(9y-5)=x then their answer will be 81y-45=x. Please explain.
If we multiply by 9 all over the equation the that is 9(9y-5)=x then their answer will be 81y-45=x. Please explain.
Ramya said:
6 years ago
Relative speed respect to 1 person and train= (x-2).
Relative speed respect to 2nd person and train= (x-4).
Dist. = speed * time.
9(x-2) = 10(x-4).
x = 22.
So, 22-2 = dist/9.
dist = 180*(5/18).
> 50.
Relative speed respect to 2nd person and train= (x-4).
Dist. = speed * time.
9(x-2) = 10(x-4).
x = 22.
So, 22-2 = dist/9.
dist = 180*(5/18).
> 50.
Kubstar said:
6 years ago
@Ramya.
Why are you subtract "2" from 22?
Why are you subtract "2" from 22?
Muttu said:
6 years ago
@Amith is well solved.
Mihir gandhi said:
5 years ago
Assume speed for s and find length means (distance)
D1=D2
(S-2)*T1=(s-4)*T2.
(S-2)*9/3600=(s-4)*10/3600.
(S-2)*9=(s-4)*10.
9s-18=10s-40.
10s-9s=40-18.
S=22.
So find length
L=D=(s-2)*T1.
=(22-2)*9/3600,
=20*9/3600,
=2*9/360,
=18/360,
=1/20,
=0.05km.
=50 meter.
D1=D2
(S-2)*T1=(s-4)*T2.
(S-2)*9/3600=(s-4)*10/3600.
(S-2)*9=(s-4)*10.
9s-18=10s-40.
10s-9s=40-18.
S=22.
So find length
L=D=(s-2)*T1.
=(22-2)*9/3600,
=20*9/3600,
=2*9/360,
=18/360,
=1/20,
=0.05km.
=50 meter.
Vickey pandy said:
5 years ago
Same direction =>2-4=2.
2*(5/18)= 5/9,
D = S*T.
D = (5/9)*10*9,
D = (5/9)*90,
D = 50.
2*(5/18)= 5/9,
D = S*T.
D = (5/9)*10*9,
D = (5/9)*90,
D = 50.
Mukundan said:
5 years ago
@Mancy.
Good Explanation. Thanks.
Good Explanation. Thanks.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers