There is a pool of water, which can hold up to 30 liters of water. It can be filled in 6 minutes with the water inlet pipe, and can be drained in 24 minutes with the drain pipe.
有一池水，最多能装30升水，用进水管注水6分钟可以注满，用放水管放水，24分钟可以放完，现水池空着，两管同时开放多少分钟可以吧水池注满．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 24</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/6) - (1/24)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / (1/8)</gadget>
<output>8</output>

<result>8</result>