It takes 10 hours for a master to process a batch of parts alone, and 15 hours for an apprentice to process alone. How many hours will it take for the master and apprentice to process this batch of parts together?
一批零件师傅单独加工要10小时，徒弟单独加工要15小时，师徒共同加工这批零件的要多少小时？
<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>