Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 17)
17.
A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:
Answer: Option
Explanation:
| Speed = |  |
78 x | 5 |  |
m/sec | = | |
65 | |
m/sec. |
| 18 | 3 |
Time = 1 minute = 60 seconds.
Let the length of the tunnel be x metres.
| Then, | |
800 + x | |
= | 65 |
| 60 | 3 |
3(800 + x) = 3900
x = 500.
Discussion:
52 comments Page 4 of 6.
Narasimha said:
1 decade ago
Hi friends,
If tunnel is x metres
1 mint=60sec
800+x=78*(5/18)60
Solve this and get the ans
Length = Speed*Time
If tunnel is x metres
1 mint=60sec
800+x=78*(5/18)60
Solve this and get the ans
Length = Speed*Time
Gai3 said:
1 decade ago
Thank you ambika.
Deva said:
1 decade ago
I DIDNOT understand this example
A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:
A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:
Subham baksi said:
1 decade ago
Why (800+x) /60? Why divided 60 is not coming in my mind?
Ramesh said:
1 decade ago
Speed of train: 78kn/hr=78*(5/18)=21.67m/sec
Distance=800m
Time=60sec
d=s*t
800+x=21.67*60
x=1300.2-800=500
Distance=800m
Time=60sec
d=s*t
800+x=21.67*60
x=1300.2-800=500
Kannika said:
1 decade ago
Why we are adding train length to the tunnel length?
Pradnyashree said:
1 decade ago
If we do 3(800+x)= 60*65,
3*800+3x=3900,
2400+3x=3900
3x=3900-2400
3x=500
x=166.66
3*800+3x=3900,
2400+3x=3900
3x=3900-2400
3x=500
x=166.66
Ranjani said:
1 decade ago
Length of the tunnel = x
length of the train = 800
relatively (x+800)
-----------------------
train crosses the platform 78 km/hr , we have to convert km/hr to m/s so the formula is 5/18 i.e., 78*(5/18)=65/3.
formula for calculatind the distance is
DISTANCE= SPEED*TIME
TIME is given as 1min i.e., 60 sec
SPEED =65/3
distance = 65/3 * 60
distance = 1300
relative length (x+800) = 1300
x = 1300- 800
therefore x= 500
length of the train = 800
relatively (x+800)
-----------------------
train crosses the platform 78 km/hr , we have to convert km/hr to m/s so the formula is 5/18 i.e., 78*(5/18)=65/3.
formula for calculatind the distance is
DISTANCE= SPEED*TIME
TIME is given as 1min i.e., 60 sec
SPEED =65/3
distance = 65/3 * 60
distance = 1300
relative length (x+800) = 1300
x = 1300- 800
therefore x= 500
Anusha said:
1 decade ago
@Kannika
We are adding train length to the tunnel length, because we have to consider the total length so we have to take this.
We are adding train length to the tunnel length, because we have to consider the total length so we have to take this.
Uday said:
1 decade ago
I do not understand what is the meaning of crossing a tunnel you understand. I think it should mean the moment train head enters the tunnel till its TAIL comes out one can not consider the train is out of tunnel if its head just come out.
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