pool is equipped with a discharge pipe and a drain pipe. Opening the water pipe alone can fill the empty pool in 8 hours, and opening the drain pipe alone can empty the full pool in 10 hours. If the pool is empty at the beginning, open the drain pipe for 5 hours Open the drain pipe again, how long will the pool just fill with water?
一个水池装有一个放水管和一个排水管，单开放水管8小时可将空池灌满，单开排水管10小时可将满池水排空，如果一开始是空池，打开放水管5小时后又打开排水管，再过多长时间池内刚好灌满水？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) * 5</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">1 - (5/8)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/8) - (1/10)</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(3/8) / (1/40)</gadget>
<output>15</output>

<result>15</result>