A tap can fill a tank in 15 minutes. Another tap can empty it in 20 minutes

A tap can fill a tank in 15 minutes. Another tap can empty it in 20 minutes. Initially the tank is empty, if both the taps start functioning at the same time, when with the tank become full?
A. 1 hour
B. 3 hours
C. 2 hours
D. 4 hours

Anurag Mishra Professor Asked on 29th February 2016 in Maths.
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1 Answer(s)

Answer: (A) 1 hour 

Solution:-
A tap can fill a tank = 15 min
Therefore, A tap can fill a tank in a min = 1/15

Another tap can  empty same tank = 20 min
Therefore, Another tap can empty a same tank = 1/20

If both the taps start functioning at the same time, 
Then, time taken by both tap to fill tank in a min = 1/15 – 1/20
 = (4 – 3)/60
 = 1/60

Both tank fill the tank = 60 min. 

Hence, the correct answer is option (A) 1 hour. 

Anurag Mishra Professor Answered on 1st March 2016.
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