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:
54 comments Page 5 of 6.
Sumana said:
1 decade ago
Why we convert 78 meter into seconds?
Manju said:
1 decade ago
5/18 means?
Smith said:
1 decade ago
Train speed 7800m/60m = 1300m.
Length of tunnel is 1300-800 = 500.
Its very simple.
Length of tunnel is 1300-800 = 500.
Its very simple.
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.
Izaan prince said:
1 decade ago
Let the speed of tunnel is x.
Length of train is = 800m
Speed of train is = 78km/hr.
Speed in m/s = 78*5/18
Time of crossing tunnel is 1min.
1 min is 60s.
We are finding the length of tunnel = ?
800+x = 78*5/18*60
x = 500
Length of train is = 800m
Speed of train is = 78km/hr.
Speed in m/s = 78*5/18
Time of crossing tunnel is 1min.
1 min is 60s.
We are finding the length of tunnel = ?
800+x = 78*5/18*60
x = 500
John said:
1 decade ago
Can I know from where did 5/18 came?
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.
Sampanna said:
1 decade ago
From where did that 5 upon 18 came.
Viral said:
1 decade 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.
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