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 3 of 6.
Siva said:
1 decade ago
If the question is to find the length of the train, then how to solve it?
Harshad said:
1 decade ago
@Siva.
The length of the train is the distance.
In our case its (x - 1.25) x 8.4 OR (x - 1.5) x 8.5.
When we equate we got x = 22.5.
So substitute in any equation.
And we get length as 178.5 m.
The length of the train is the distance.
In our case its (x - 1.25) x 8.4 OR (x - 1.5) x 8.5.
When we equate we got x = 22.5.
So substitute in any equation.
And we get length as 178.5 m.
Nitishkumar said:
1 decade ago
The two train and man are moving in same direction.
So the relative speed = x-5.4 & another we write that other man, x-4.5 train length is constant that's by distance will be equal.
So the relative speed = x-5.4 & another we write that other man, x-4.5 train length is constant that's by distance will be equal.
BALIRAM said:
1 decade ago
When add the speed and when subtract the speed in the case two train.
Yubaraj said:
10 years ago
If trains are in same direction the speed should be subtracted otherwise add.
Jayasree said:
9 years ago
Can anyone explain the first step?
= 4.5 km/hr = 4.5*5/18.
= 4.5 km/hr = 4.5*5/18.
Sourav maity said:
9 years ago
Why you take 5/18?
Arsh said:
9 years ago
Can anybody tell me the shortcut method because in entrance exam there is not much time to make and solve equations?
John said:
9 years ago
@Saurav 5/18 is the common unit to convert speed by km/hr to m/s. But the question is distance calculated can't be equal because both the persons having different speed and most probably they can't be at the equal level or abreast.
Maggi said:
9 years ago
How 2.25 came? Please tell me.
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