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.
Pradnyashree said:
1 decade ago
If we do 3(800+x)= 60*65,
3*800+3x=3900,
2400+3x=3900
3x=3900-2400
3x=500
x=166.66
3*800+3x=3900,
2400+3x=3900
3x=3900-2400
3x=500
x=166.66
Ranjani said:
1 decade ago
Length of the tunnel = x
length of the train = 800
relatively (x+800)
-----------------------
train crosses the platform 78 km/hr , we have to convert km/hr to m/s so the formula is 5/18 i.e., 78*(5/18)=65/3.
formula for calculatind the distance is
DISTANCE= SPEED*TIME
TIME is given as 1min i.e., 60 sec
SPEED =65/3
distance = 65/3 * 60
distance = 1300
relative length (x+800) = 1300
x = 1300- 800
therefore x= 500
length of the train = 800
relatively (x+800)
-----------------------
train crosses the platform 78 km/hr , we have to convert km/hr to m/s so the formula is 5/18 i.e., 78*(5/18)=65/3.
formula for calculatind the distance is
DISTANCE= SPEED*TIME
TIME is given as 1min i.e., 60 sec
SPEED =65/3
distance = 65/3 * 60
distance = 1300
relative length (x+800) = 1300
x = 1300- 800
therefore x= 500
Anusha said:
1 decade ago
@Kannika
We are adding train length to the tunnel length, because we have to consider the total length so we have to take this.
We are adding train length to the tunnel length, because we have to consider the total length so we have to take this.
Sumana said:
1 decade ago
Why we convert 78 meter into seconds?
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.
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.
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