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 3 of 6.
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.
Sampanna said:
1 decade ago
From where did that 5 upon 18 came.
Viral said:
10 years ago
Distance/Speed = Time.
800 + Length of Tunnel/21.6666667 = 60 Secs.
Length of Tunnel = 60*21.666667-800.
Length of Tunnel = 1300 - 800.
Length of Tunnel = 500.
Note:
Distance = Length of Train (Given) + Length of Tunnel (Asked to Find).
Speed = 78 kmph (Given). We convert that into meters per second. Therefore 78*5/18 = 21.6666667.
800 + Length of Tunnel/21.6666667 = 60 Secs.
Length of Tunnel = 60*21.666667-800.
Length of Tunnel = 1300 - 800.
Length of Tunnel = 500.
Note:
Distance = Length of Train (Given) + Length of Tunnel (Asked to Find).
Speed = 78 kmph (Given). We convert that into meters per second. Therefore 78*5/18 = 21.6666667.
Subhadeep Saha said:
10 years ago
Why we are converting into seconds we could have converted into meter/minutes, if the train is going in 75km/hr speed means train is going 78000 meters in 60 minutes from here we can execute how much distance the train covers in 1 minutes, after that by subtracting the train length we can execute the tunnel length.
Sandeep kumar said:
10 years ago
It is simple- as a train covers 78 km in one hour so train covers 78000 meter (78*1000 meter) in 60 minuet, so train cover in one minutes is 78000/60=1300 meter train itself length 800 meter so tunnel length = total distance cover by train-train length, 1300-800 = 500 meter.
Parameshwar said:
10 years ago
May I know, how we got 5/18?
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.
Manju said:
10 years ago
5/18 means?
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)
Karthik said:
9 years ago
How the 5/18 came?
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