Fill water into the water tank, open pipe A alone, the empty tank can be filled with water in 10 minutes, open pipe B alone, and the full tank can be drained in 15 minutes. How many minutes can the empty tank be filled with water when the two pipes are opened together?
往水箱里注水，单开甲管，10分钟可将空箱注满水，单开乙管，15分钟可将满箱水排完．两管齐开，多少分钟可将空箱注满水？
<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>