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.
Naveen said:
6 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:
6 years ago
Why need to convert 1 minute to 60 seconds?
ABDUL WAHAB SHAH said:
6 years ago
Last step:
3(800 + x) = 3900.
2400 + 3x = 3900.
3x = 3900 - 2400.
3x = 1500.
x = 1500/3.
x = 500.
3(800 + x) = 3900.
2400 + 3x = 3900.
3x = 3900 - 2400.
3x = 1500.
x = 1500/3.
x = 500.
(5)
Adnan said:
5 years ago
To understand why we use 5/18 so i clarify that to convert km into m we multiply with 1000 and from hours to second we divided by 60*60.
Hence we get 5/18.
Suppose to change 1 km /hr into metre /sec.
1 * 1000/60 * 60 = 5/18.
Hence we get 5/18.
Suppose to change 1 km /hr into metre /sec.
1 * 1000/60 * 60 = 5/18.
(2)
Saikat said:
4 years ago
=> x+800/60 = 78 * 5/18,
=> x+800/60 = 65/3,
=> x+800 = 65 * 60/3,
=> x+800 = 1300,
=> x = 1300-800,
=> x = 500.
=> x+800/60 = 65/3,
=> x+800 = 65 * 60/3,
=> x+800 = 1300,
=> x = 1300-800,
=> x = 500.
(1)
Khushi said:
4 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.
Joel said:
3 years ago
@Pradnyashree.
How is 3900-2400 =500?
It's 1500. Can anyone explain that?
How is 3900-2400 =500?
It's 1500. Can anyone explain that?
(2)
Somil kumar bhadula said:
3 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?
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)
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)
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