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 6 of 11.
Karuna said:
9 years ago
What is that 5/18 and why should we take that?
Akhilesh Mehta said:
9 years ago
@Karuna.
It is for converting the speed Km/h to m/sec.
It is for converting the speed Km/h to m/sec.
Raja said:
9 years ago
@K. Anitha.
I didn't get your last step. Please explain.
I didn't get your last step. Please explain.
Sathees said:
9 years ago
Equ 1 is => x = (9y - 5) /9 * 9 = 9 y - 5 => 5 = 9y - 5.
Equ 2 is => x = (9y - 10) /9 *10.
9 x = (9y - 10) * 10.
9x = (90y - 100) => 100 = 90y - 9 x.
90y - 9 x = 100 (person - 2 is walk fast).
90y - 10 x= 50 (equ 2 is multiplied by 10).
------------------
x = 50.
------------------
Equ 2 is => x = (9y - 10) /9 *10.
9 x = (9y - 10) * 10.
9x = (90y - 100) => 100 = 90y - 9 x.
90y - 9 x = 100 (person - 2 is walk fast).
90y - 10 x= 50 (equ 2 is multiplied by 10).
------------------
x = 50.
------------------
Krishna said:
9 years ago
@All.
Please anyone give the answer of Durga's question, I have the same question.
Please anyone give the answer of Durga's question, I have the same question.
Sumaira said:
9 years ago
@Kapil.
Thanks for the trick I tried to simplify more.
(S - 2) * 5/18 = L/9..........(1)
Similarly
(S - 4) * 5/18 = L/10..........(2)
9(s - 2) = 10(s - 4)
9s - 18 = 10s - 40
S = 40-18
S = 22
Put value of s in any one equal , suppose in (1)
(22 - 2) * 5/18 = L/9.
L = 50.
Thanks for the trick I tried to simplify more.
(S - 2) * 5/18 = L/9..........(1)
Similarly
(S - 4) * 5/18 = L/10..........(2)
9(s - 2) = 10(s - 4)
9s - 18 = 10s - 40
S = 40-18
S = 22
Put value of s in any one equal , suppose in (1)
(22 - 2) * 5/18 = L/9.
L = 50.
Anu malik said:
9 years ago
Can't understand, please, tell me how to explain it in short cut method?
Anagha said:
9 years ago
(4-2) * (5/18) * 9 * 10 = 50.
Mou444276 said:
9 years ago
@Anagha.
Why 9 *10 or not 19?
Why 9 *10 or not 19?
Vikas3692 said:
9 years ago
@Anagha,
Please explain why 9 * 10?
Please explain why 9 * 10?
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