Pipe A can fill a tank in 12 hours. Due to a leak at the bottom, it takes 18 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?  Choose the most appropriate option.
A) 36 B) 87 C) 40 D) 37 E) 86
Let the leak can empty the full tank in x hours 1/12 - 1/x = 1/18   =&gt; 1/x = 1/12 - 1/18 = (3 - 2)/36 = 1/36   =&gt; x = 36.   36nswer: 36
<result>A</result>
Pipe A can fill a tank in 12 hours. Due to a leak at the bottom, it takes 18 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?