Processing - a batch of parts, A alone 10 hours to complete, B alone 15 hours to complete. How many hours can A and B cooperate to complete?
加工-批零件，甲单独做10小时完成，乙单独做15小时完成．甲、乙合作多少小时可以完成．
<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>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>