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 5 of 6.
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
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
Kannika said:
1 decade ago
Why we are adding train length to the tunnel length?
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
Subham baksi said:
1 decade ago
Why (800+x) /60? Why divided 60 is not coming in my mind?
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:
Gai3 said:
1 decade ago
Thank you ambika.
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
Sugi said:
1 decade ago
Hi friends how that 3900 came ?
Ambika said:
1 decade ago
Hi Thanu,
It's so simple ,Frist we convert km/hr in to m/sec becase train length is given in metres, so multiple speed with 5/18; Then it becomes into 78*5/18=65/3m/sec
Now we can find the length of tunnels say it as "x"metres.
use formula
speed=(length of tunnel+length of train)/60;where 1 minute=60 sec
x+800/60=65/3;After calculation x=500
It's so simple ,Frist we convert km/hr in to m/sec becase train length is given in metres, so multiple speed with 5/18; Then it becomes into 78*5/18=65/3m/sec
Now we can find the length of tunnels say it as "x"metres.
use formula
speed=(length of tunnel+length of train)/60;where 1 minute=60 sec
x+800/60=65/3;After calculation x=500
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers