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:
108 comments Page 5 of 11.
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.
Anurag Sinha said:
8 years ago
The simple ans just use this formula:-
Length of the train=(diff in speed *t1*t2)/diff in time,
Length of the train=(4*5*9*10/18*1)=50 m).
Length of the train=(diff in speed *t1*t2)/diff in time,
Length of the train=(4*5*9*10/18*1)=50 m).
Angad yadav said:
1 decade ago
Because the man who walking with the velocity greater, the train take maximum time to overtake him than the other guy.
Karanam Sai Charan said:
9 months ago
Use this formulae:
L = ((T1*T2)/T2-T1) * ( S2 - S1),
= ((9*10)/10-9) * (4-2),
= 90 * 2(5/18),
= 50.4 or 50.
L = ((T1*T2)/T2-T1) * ( S2 - S1),
= ((9*10)/10-9) * (4-2),
= 90 * 2(5/18),
= 50.4 or 50.
(3)
Kadher said:
1 decade ago
We can take either s-s1 or s-s2.
If we substitute in s-s2.
Then,
(110/18)-(20/18)=(x/10)
(90/18)=x/10
5=x/10
x=50.
If we substitute in s-s2.
Then,
(110/18)-(20/18)=(x/10)
(90/18)=x/10
5=x/10
x=50.
Nady said:
1 decade ago
(x/(y-5/9)) = 9.
Now cross multiply this.
So we get x = 9*(y-5/9) i.e.,x = 9y-5 and do the same for other one too.
Now cross multiply this.
So we get x = 9*(y-5/9) i.e.,x = 9y-5 and do the same for other one too.
Jeevitha said:
1 decade ago
@Kapil.
Your method is easy. Thanks for it. But at last step it is:
((55/9)-(5/9))*9=50m.
CNA finish off this way.
Your method is easy. Thanks for it. But at last step it is:
((55/9)-(5/9))*9=50m.
CNA finish off this way.
Durga said:
1 decade ago
Please anyone can simplify this step?
9y-x=5 and 90y-9x=100. I can't understand this. How will we get x=50?
9y-x=5 and 90y-9x=100. I can't understand this. How will we get x=50?
S.Banerjee said:
9 years ago
Is there any shortcut method to solve this problem? Please help me if there is any shortcut to solve easily.
Soumen said:
8 years ago
Lenth=(diff between speed * t1 * t2)/diff in time.
Lenth=(2 * 5 * 9 * 10)/(1 * 18),
= 50m.
Lenth=(2 * 5 * 9 * 10)/(1 * 18),
= 50m.
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