A pool is equipped with two water pipes A and B, and the two pipes are opened together for 10 hours to fill the pool. It takes 15 hours to open pipe B to fill the pool, and how many hours to open pipe A to fill the pool.
一个水池装有甲、乙两个水管，两管齐开10小时注满水池．单开乙管15小时注满水池，单开甲管多少小时注满水池．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">(1/10) - (1/15)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>