A batch of parts can be completed by A alone in 15 hours, and by B alone in 10 hours. Now A and B are working together, how many hours can it be completed?
一批零件由甲单独加工15小时能完成，由乙单独加工10小时能完成．现在由甲乙两人合做，几小时可以完成？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

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

<gadget id="calculator">(1/15) + (1/10)</gadget>
<output>1/6 = around 0.166667</output>

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

<result>6</result>