Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 20)
20.
A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train?
Answer: Option
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
| Then, | x | = 8  x = 8y |
| y |
| Now, | x + 264 | = y |
| 20 |
8y + 264 = 20y
y = 22.
 Speed = 22 m/sec = |
 |
22 x | 18 |  |
km/hr = 79.2 km/hr. |
| 5 |
Discussion:
46 comments Page 3 of 5.
Rakshi said:
9 years ago
Hi, I can't understand. Why are we taking time as the difference of both?
Jamir said:
9 years ago
Relative time = 20 - 8
= 12
Then,
Speed = Distance/ time
= 264/12
= 22 m/sec
= 22 *15/5 km/h.
= 79.2 km/ h.
Answer = 79.2 km/ h.
= 12
Then,
Speed = Distance/ time
= 264/12
= 22 m/sec
= 22 *15/5 km/h.
= 79.2 km/ h.
Answer = 79.2 km/ h.
Souvanik saha said:
9 years ago
Last one is very smart and short method. Actually I was also doing this. But I forgot to convert m/s to km/hr. For that my answer was 22 m/s. So I thought that I was wrong. Because the answer given in km/hr.
Total distance = 284.
And time taken (20-8) = 12 because it is in same direction.
And now Speed = Distance/Time.
= 284/12.
= 22 m/s.
= 22*18/5 km/hr.
= 79.2 km/hr.
Total distance = 284.
And time taken (20-8) = 12 because it is in same direction.
And now Speed = Distance/Time.
= 284/12.
= 22 m/s.
= 22*18/5 km/hr.
= 79.2 km/hr.
(3)
Vignesh said:
10 years ago
Don't go complex one, we need Speed = Distance/Time.
Total distance = 284.
Time taken to cross is 12 sec (20-8).
Speed = 22 m/s or 79.2 km/hr.
Total distance = 284.
Time taken to cross is 12 sec (20-8).
Speed = 22 m/s or 79.2 km/hr.
(1)
Rahaman Khan said:
10 years ago
1) Train cross the pole in 8 sec.
Speed = Distance/Time.
Assume the train speed is x and length of train be y.
x = y/8 or y = 8x.
2) Train cross the bride which is 264mts long 20 sec.
x = (264+y)/20.
20x = 264+8x because y = 8x in above.
Solving the above equation we get speed is 22m/sec.
Finally convert the m/sec to km/hr.
22*18/5 = 79.2 km/hr.
Speed = Distance/Time.
Assume the train speed is x and length of train be y.
x = y/8 or y = 8x.
2) Train cross the bride which is 264mts long 20 sec.
x = (264+y)/20.
20x = 264+8x because y = 8x in above.
Solving the above equation we get speed is 22m/sec.
Finally convert the m/sec to km/hr.
22*18/5 = 79.2 km/hr.
Anjani said:
10 years ago
Why we take 8 sec why don't we consider 20 sec?
Vamsy said:
1 decade ago
@Hussaian.
1) km/hr to m/s conversion:
km/hr = a x 5km/18hr.
2) m/s to km/hr conversion:
m/s = a x 18km/5hr.
1) km/hr to m/s conversion:
km/hr = a x 5km/18hr.
2) m/s to km/hr conversion:
m/s = a x 18km/5hr.
Hussain said:
1 decade ago
How we got 18/5? Can any one explain me clearly?
Subham kumar said:
1 decade ago
A train passes telegraph post is 40 seconds morning at a rate of 36 km/hr. Then the length of the train is: 8.
Neelam said:
1 decade ago
How you people got 3x = 528?
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