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 3 of 11.
Nisma said:
5 years ago
There is a simple formula to do this type of questions.
If a train covers 2 persons with speed S1 and S2 in time T1 and T2, then the length of train is:
(S1-S2 ÷ T1-T2) * T1 * T2.
So applying it in this question;
{(4-2)5/18÷10-9} * 10 * 9 =50m.
Note:(4-2) is multiplied by 5/18 so as to convert km to m.
If a train covers 2 persons with speed S1 and S2 in time T1 and T2, then the length of train is:
(S1-S2 ÷ T1-T2) * T1 * T2.
So applying it in this question;
{(4-2)5/18÷10-9} * 10 * 9 =50m.
Note:(4-2) is multiplied by 5/18 so as to convert km to m.
Pooja said:
5 years ago
@All.
Why they do not subtract speed first, then convert into m/sec?
Can anyone explain, please?
Why they do not subtract speed first, then convert into m/sec?
Can anyone explain, please?
Sumit said:
5 years ago
@Ramya.
Why don't you use x-4 equation?
Why don't you use x-4 equation?
Raksha said:
5 years ago
I did not get it properly. Could someone explain me briefly?
Mukundan said:
5 years ago
@Mancy.
Good Explanation. Thanks.
Good Explanation. Thanks.
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.
Vishal k. Ramteke said:
5 years ago
Its pretty simple just follow the short trick i.e we know that,
Distance= Time*speed.
So,
Distance=9*10*2*5/18 just solve this you will get the answer in a minute i.e 50 m.
Distance= Time*speed.
So,
Distance=9*10*2*5/18 just solve this you will get the answer in a minute i.e 50 m.
(1)
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.
Muttu said:
6 years ago
@Amith is well solved.
Kubstar said:
6 years ago
@Ramya.
Why are you subtract "2" from 22?
Why are you subtract "2" from 22?
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