There are two water pipes in a pool. If pipe A is opened alone, the pool can be filled in 10 minutes; if pipe B is opened alone, the pool can be completely drained in 15 minutes. How many minutes can the empty pool be filled with two pipes?
一个水池有两个水管，单开甲管，10分可将水池只注满；单开乙管，15分可将一池水放完．两管齐开，几分可将空池注满？
<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>