Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 16)
16.
A train travelling at a speed of 75 mph enters a tunnel 3
miles long. The train is 
mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges?
miles long. The train is mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges?Answer: Option
Explanation:
| Total distance covered |
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 Time taken |
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| = 3 min. |
Discussion:
129 comments Page 2 of 13.
Amit said:
1 decade ago
Actually time and distance two different units.we want to find the time of crossing the tunnel. Speed is given in the form of 75 miles/hour so our concern only with hour not distance so change hour to minute and then calculate ur answer.
Total length =7/2 + 1/4 = 15/4 miles
Speed = 75 mile/hour = (75/60)miles/minute
Now time taken is distance / speed = (15/4) / (75/60) = 15*60/4*75 =3 minute.
Total length =7/2 + 1/4 = 15/4 miles
Speed = 75 mile/hour = (75/60)miles/minute
Now time taken is distance / speed = (15/4) / (75/60) = 15*60/4*75 =3 minute.
Sudarsan said:
1 decade ago
Can any body explain, in the particular question my doubt is length is miles per hour and also unit of speed is also given in miles. Whether the length-speed or length-time is to be same unit of measurement to calculate the third?
I was thinking length-time-speed should be either Kilometer-hour-Kph or meter-seconds-meter per second.
I was thinking length-time-speed should be either Kilometer-hour-Kph or meter-seconds-meter per second.
GOKULAKRISHNAN A B said:
3 months ago
@All.
Given, A train travelling at a speed of 75 mph enters a tunnel 3 1/2 miles long.
Here, the speed is given in miles per hour it is not meter per hour and the distance is given wrong it is 7 1/2.
Now, calculate the answer will come as 0.05 hours to convert hours to min multiplied by 60.
So, 0.05 x 60 = 3 min.
Given, A train travelling at a speed of 75 mph enters a tunnel 3 1/2 miles long.
Here, the speed is given in miles per hour it is not meter per hour and the distance is given wrong it is 7 1/2.
Now, calculate the answer will come as 0.05 hours to convert hours to min multiplied by 60.
So, 0.05 x 60 = 3 min.
Shro said:
1 decade ago
Distance is (7/2 ) + (1/4 ) = (15/4)
speed is 75mph
time= distance /speed
So time= (15/4) / 75
which can also be written as ( 15/(75*4))
So we get it as 1/20 hrs
But expected ans is in minutes.
So convert hrs into minutes.
So (1/20) * 60
which gives the final answer 3min.
Good Luck :)
speed is 75mph
time= distance /speed
So time= (15/4) / 75
which can also be written as ( 15/(75*4))
So we get it as 1/20 hrs
But expected ans is in minutes.
So convert hrs into minutes.
So (1/20) * 60
which gives the final answer 3min.
Good Luck :)
Vinit said:
1 decade ago
In question it is asked that "How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges?" so 1/4 will be added twice i.e.
Total distance would be 7/2 + 1/4 + 1/4
And Finally answer is 3.2 mins
Total distance would be 7/2 + 1/4 + 1/4
And Finally answer is 3.2 mins
Anitha said:
1 decade ago
Yes Gaurav I agree with you..
Total distance covered = 7/2(tunnel)+1/4(length of train)+1/4(length of train since the rear part is to be considered emerging)= 4 miles
So total time taken = (4 miles / 75mph ) * 60 mins
= 3.2 mins
So the answer is [C]
Total distance covered = 7/2(tunnel)+1/4(length of train)+1/4(length of train since the rear part is to be considered emerging)= 4 miles
So total time taken = (4 miles / 75mph ) * 60 mins
= 3.2 mins
So the answer is [C]
Ashu said:
8 years ago
We must add two times the distance of the train because we are just calculating the time needed to cross the tunnel if we just add one time the length of the train. So the answer must be 3.2min.
It doesn't need to explain the question that if we add only one time.
It doesn't need to explain the question that if we add only one time.
Appa rao said:
9 years ago
The answer should be option C.
Total distance covered = 7/2(tunnel) + 1/4(length of train) + 1/4(length of train since the rear part is to be considered emerging) = 4 miles.
So total time taken = (4 miles/75mph ) * 60 mins.
= 3.2 mins.
So the answer is option C.
Total distance covered = 7/2(tunnel) + 1/4(length of train) + 1/4(length of train since the rear part is to be considered emerging) = 4 miles.
So total time taken = (4 miles/75mph ) * 60 mins.
= 3.2 mins.
So the answer is option C.
Jahnavi said:
4 years ago
1meter = 0.0006 miles.
So, the conversion of meters to miles is not required.
You can directly calculate the time without changing units.
Note: The length of the train need not be taken twice. This is similar to the bridge problem (train crossing the bridge).
So, the conversion of meters to miles is not required.
You can directly calculate the time without changing units.
Note: The length of the train need not be taken twice. This is similar to the bridge problem (train crossing the bridge).
(5)
Sagnik Bhunia said:
1 year ago
Train length must be multiplied by 2 and added tunnel length to get the total distance as the problem says train starts from entering the tunnel from front to exiting the tunnel till its end.
Shouldn't it be the correct interpretation? Anyone, Please clarify.
Shouldn't it be the correct interpretation? Anyone, Please clarify.
(12)
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