pool has three water pipes A, B, and C. A, B are the water inlet pipes, and C is the drain pipe. Opening the A water pipe alone can fill the pool for 10 minutes, and opening the B water pipe alone for 15 minutes can fill the water. Open pipe C for 20 minutes to drain the water in the pool. Now open pipes A and B first. After 5 minutes, close pipe A and open pipe C. How many minutes will it take to fill the pool?
一个水池，有甲、乙、丙三个水管，甲、乙是入水管，丙是排水管，单独开甲水管10分钟可将水池注满，单独开乙水管15分钟可将水注满，单独开丙管20分钟可将全池水放完，现在先开甲、乙水管，5分钟后关上甲管，开丙管，问又经几分钟才能将水池注满？
<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">5 / 15</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/15) - (1/20)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/6) / (1/60)</gadget>
<output>10</output>

<result>10</result>