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Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 16)
Problems on Trains
16.
A train travelling at a speed of 75 mph enters a tunnel 31/2 miles long. The train is 1/4 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?
2.5 min
3 min
3.2 min
3.5 min
Answer: Option
Explanation:

Total distance covered
= ( 7 + 1 ( miles
2 4
= 15 miles.
4

Therefore Time taken
= ( 15 ( hrs
4 x 75
= 1 hrs
20
= ( 1 x 60 ( min.
20
= 3 min.

Discussion:
129 comments Page 8 of 13.
Muthumari said:   2 years ago
Speed = distance/time.
75/60(meter/min) = [ (7/2)+(1/4)] ÷ t.
t = (15/4)×(60/75),
t = 3min.
(2)
Santhosh said:   1 decade ago
I did not get any clarity, I'm fluctuating between Gaurav and Manni.

Can any one explain?
Akshay Agrawal said:   6 years ago
15/4.

(7/2 +1/4) = let take hcm of this i.e. 4.
Then, (7*2/4 +1/4),
(14+1/4)=15/4.
Uday said:   1 decade ago
In this problem we need time only that's why we are changing time only into minutes.
Prakhar Mittal said:   9 years ago
It is not clear that the speed is given in which units as Rahul Bhosale asked above.
Vishu said:   10 years ago
Time = Distance/Speed.

Time = (15/4)/75.

So how will it come like this 15/4*75?
Munesh said:   1 decade ago
Please can any one clearly explain the formation of expression.

(7/2) + (1/4).
Rahul Bhosale said:   9 years ago
Mph means mile per hour OR meter per hour?

I think mile per hour is correct.
Priyavel said:   1 decade ago
@Errer

We convert mixed fraction into proper fraction
( 3*2=6+1=7)
Gourab said:   1 decade ago
Yes aditya, you are absolutely rite, the answer should be 3. 2 min.
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