Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 28)
28.
A train overtakes two persons walking along a railway track. The first one walks at 4.5 km/hr. The other one walks at 5.4 km/hr. The train needs 8.4 and 8.5 seconds respectively to overtake them. What is the speed of the train if both the persons are walking in the same direction as the train?
Answer: Option
Explanation:
| 4.5 km/hr = |  |
4.5 x | 5 |  |
m/sec = | 5 | m/sec = 1.25 m/sec, and |
| 18 | 4 |
| 5.4 km/hr = | |
5.4 x | 5 | |
m/sec = | 3 | m/sec = 1.5 m/sec. |
| 18 | 2 |
Let the speed of the train be x m/sec.
Then, (x - 1.25) x 8.4 = (x - 1.5) x 8.5
8.4x - 10.5 = 8.5x - 12.75
0.1x = 2.25
x = 22.5
 Speed of the train = |
|
22.5 x | 18 | |
km/hr = 81 km/hr. |
| 5 |
Discussion:
54 comments Page 6 of 6.
Gowthami said:
1 decade ago
Hi Deepika
The last step is converting m/sec to km/hr.
But i am not understanding how can the dist be equated?
(x - 1.25) x 8.4 = (x - 1.5) x 8.5
can any one explain it plz.
The last step is converting m/sec to km/hr.
But i am not understanding how can the dist be equated?
(x - 1.25) x 8.4 = (x - 1.5) x 8.5
can any one explain it plz.
Deepika said:
1 decade ago
Please explain me only the last step.
Nitesh Nandwana said:
1 decade ago
Hi Chanda,
If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then:
(A's speed) : (B's speed) = (b : a)
If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then:
(A's speed) : (B's speed) = (b : a)
Chanda said:
1 decade ago
Please some one explain me in detail. Thank you
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