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 2 of 6.
Nik said:
9 years ago
Hi.
Distance/time = Speed.
Let length of the tunnel be x.
Then Distance = Lenth of Train + Lenght of the tunnel.
ie. (800+x)/60 = (65/3).
Now 800 + x = (65/3)*60.
ie 800 + x = 1300.
x = 1300 - 800.
x = 500.
Distance/time = Speed.
Let length of the tunnel be x.
Then Distance = Lenth of Train + Lenght of the tunnel.
ie. (800+x)/60 = (65/3).
Now 800 + x = (65/3)*60.
ie 800 + x = 1300.
x = 1300 - 800.
x = 500.
(1)
Abdul azees said:
3 years ago
Easy way
Distance = 800 meter,
Speed = 78 km/hr,
Time =1 min,
Need to find 800+x,
speed = 78km/hr~1300 meter/minute,
800+x = 1300 *1 as per (D = S * T formula),
x = 1300 - 800.
x = 500 meters.
That's all.
Distance = 800 meter,
Speed = 78 km/hr,
Time =1 min,
Need to find 800+x,
speed = 78km/hr~1300 meter/minute,
800+x = 1300 *1 as per (D = S * T formula),
x = 1300 - 800.
x = 500 meters.
That's all.
(6)
Jay said:
8 years ago
Speed=78 km/hr
=78 x 5/18 = 65/3 m/sec
Time = i min = 60 sec
Let the length of he tunnel be x metres
but here already given 800 metres
Therefore d=s x t
So,
800x=65/3 x 60
800x= 1300
x= 1300 - 800
x= 500.
=78 x 5/18 = 65/3 m/sec
Time = i min = 60 sec
Let the length of he tunnel be x metres
but here already given 800 metres
Therefore d=s x t
So,
800x=65/3 x 60
800x= 1300
x= 1300 - 800
x= 500.
Naman said:
8 years ago
What if we turn the speed into m/s first, like.
78 x (5/18)=> 65/3 => 15,
then use formula D = S*T.
then we get,
D+800 = 15 * 60.
D+800 = 900,
D = 100,
Is this wrong ?
why 2 different answer?
78 x (5/18)=> 65/3 => 15,
then use formula D = S*T.
then we get,
D+800 = 15 * 60.
D+800 = 900,
D = 100,
Is this wrong ?
why 2 different answer?
Ravitheja said:
1 decade ago
Speed of Train = 78kmph.
Speed of Train in Meters/Min =78000/60 = 1300 mpm.
Length of the tunnel be x, Speed = x+800 m/1 min.
There fore calculating for x, x+800/1 = 1300/1 = x = 500 m.
Speed of Train in Meters/Min =78000/60 = 1300 mpm.
Length of the tunnel be x, Speed = x+800 m/1 min.
There fore calculating for x, x+800/1 = 1300/1 = x = 500 m.
Romon said:
1 decade ago
Train travels @78kmph.
So in 1 minute it goes 78km/60min = 1.3 km per minute or 1300mtr.
Then length of tunnel = (Total length - Length of the Train).
= 1300mtr - 800mtr.
= 500.
So in 1 minute it goes 78km/60min = 1.3 km per minute or 1300mtr.
Then length of tunnel = (Total length - Length of the Train).
= 1300mtr - 800mtr.
= 500.
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:
Harish said:
1 decade ago
@Pradnyashree.
If we do 3(800+x) = 60*65,
3*800+3x = 3900,
2400+3x = 3900,
3x = 3900-2400,
3x = 500.
x = 166.66 you are wrong.
Here 3x = 3900-2400 = 1500.
x = 500.
If we do 3(800+x) = 60*65,
3*800+3x = 3900,
2400+3x = 3900,
3x = 3900-2400,
3x = 500.
x = 166.66 you are wrong.
Here 3x = 3900-2400 = 1500.
x = 500.
Shivam shah said:
10 years ago
Why length is taken as 800 meters here and not 1600? Came to my mind as because when head enters and tail comes out, so length should be considered as 1600.
Bunny said:
5 months ago
Speed = 78 * 1000/60 = 1300.
Total length = length of tunnel + length of train,
1300 = length of tunnel + 800.
Length of the train = 1300-800 = 500.
Total length = length of tunnel + length of train,
1300 = length of tunnel + 800.
Length of the train = 1300-800 = 500.
(1)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers