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 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 3 of 13.

Priyavel said:   1 decade ago
@Errer

We convert mixed fraction into proper fraction
( 3*2=6+1=7)

Pasha4u said:   1 decade ago
Please can any one explain it ?

Sree said:   1 decade ago
Please explain clearly how 7/2?

Viswam said:   1 decade ago
See this link: http://www.mathsisfun.com/mixed-fractions.html

Gaurav said:   1 decade ago
I think the total distance = 7/2 + 1/4 + 1/4 = 4 miles as the summation of length of the tunnel, length of train when it enters and length of train when it emerges out should be taken.

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]

Manni said:   1 decade ago
It will be 3mins.

Because total distance is 7/2 (tunnel) +1/4 (train).

When train starts entering tunnel there is nothing inside so why take 2 times.

Santhosh said:   1 decade ago
I did not get any clarity, I'm fluctuating between Gaurav and Manni.

Can any one explain?

Swetha said:   1 decade ago
I didn't understand? can any one explain ?

Swetha said:   1 decade ago
Why don't we convert miles into meter in this problem? I'm very confused. Can anyone explain the solution clearly? please.


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