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 3 of 6.
Sahdev said:
9 years ago
3(800+x) =3900 = 1500.
Then x = 500?
Then x = 500?
Sarang said:
8 years ago
Distance =speed * time,
D=78km/h*1minute,
D=78*5/18*60.
D=78*.277*60.
D=21.6*60= 1300-800= 500.
D=78km/h*1minute,
D=78*5/18*60.
D=78*.277*60.
D=21.6*60= 1300-800= 500.
Khushi said:
5 years ago
@All.
Please correct me, if my calculation is wrong.
If we convert 78 km/hr into m/s.
So,
78 * 5/18.
390/18.
21.6 m/s.
Now if we put these value.
x + 800/60=21.6,
x + 800= 60 * 21.6,
x+800= 1296,
x= 1296 - 800.
x= 496.
Anyone please clarify this and explain with the correct answer.
Please correct me, if my calculation is wrong.
If we convert 78 km/hr into m/s.
So,
78 * 5/18.
390/18.
21.6 m/s.
Now if we put these value.
x + 800/60=21.6,
x + 800= 60 * 21.6,
x+800= 1296,
x= 1296 - 800.
x= 496.
Anyone please clarify this and explain with the correct answer.
Arushi said:
8 years ago
I am not getting, how come 5/18? Please, someone explain me.
Roobha said:
8 years ago
1km = 1000m,
1hr = 3600sec.
Convert,
Km/hr=m/sec.
= 1000/3600m/sec,
= 5/18m/sec.
1hr = 3600sec.
Convert,
Km/hr=m/sec.
= 1000/3600m/sec,
= 5/18m/sec.
Naveen said:
8 years ago
X+800 = 78 * 5/18 * 60,
X+800 = 13*5/3 *60,
X+800 = 13*5*20,
X+800 = 65*20,
X+800 = 1300,
X = 1300-800,
X = 500.
X+800 = 13*5/3 *60,
X+800 = 13*5*20,
X+800 = 65*20,
X+800 = 1300,
X = 1300-800,
X = 500.
Rohan said:
7 years ago
Why need to convert 1 minute to 60 seconds?
Somil kumar bhadula said:
4 years ago
3(800+x) = 1900
2400+3x = 1900
3x = 2400-1900,
3x = 500.
I understand the thing. But where the 3x goes?
Can somebody tell me?
2400+3x = 1900
3x = 2400-1900,
3x = 500.
I understand the thing. But where the 3x goes?
Can somebody tell me?
Ramya said:
1 decade ago
78 is in kmph but answer is in meter so we should convert km to meter by 5/18 is the formula.
If you want to convert meter into km by 18/5.
If you want to convert meter into km by 18/5.
Ambika said:
2 decades 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
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