pool has an inlet pipe and a drain pipe. Opening the water inlet pipe alone can fill the pool in 4 minutes, and opening the drain pipe alone can drain the full pool in 6 minutes. There is (1/3) dirty water in the pool. Master Li has to drain the dirty water first, but he forgot to turn off the drainpipe when pouring clean water. How long will it take to fill it with clean water?
一个水池装有一个进水管和一个排水管．单开进水管4分钟可以把水池注满，单开排水管6分钟可把满池水排完．现池内有(1/3)的脏水，李师傅要先排尽脏水，但注清水时他忘了关排水管，那么共需多少时间才能注满清水？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

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

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) - (1/6)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / (1/12)</gadget>
<output>12</output>

<gadget id="calculator">2 + 12</gadget>
<output>14</output>

<result>14</result>