Pipe A can fill a tank in 4 hours. Due to a leak at the bottom, it takes 8 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?
Choose the correct option
A) 13  B) 17  C) 18  D) 8  E) 12
Let the leak can empty the full tank in x hours 1/4 - 1/x = 1/8   =&gt; 1/x = 1/4 - 1/8 = (2 - 1)/8 = 1/8   =&gt; x = 8.   Answer: 8
<result>D</result>
Pipe A can fill a tank in 4 hours. Due to a leak at the bottom, it takes 8 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?