A tap can fill a tank in 15 minutes. Another tap can empty it in 20 minutes
Answer: (A) 1 hour
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
Both tank fill the tank = 60 min.
Hence, the correct answer is option (A) 1 hour.