To process a batch of parts, it takes 4 days for the master to process alone, and 6 days for the apprentice to repair alone. If the master and the apprentice work together, how many days can the parts be processed?
加工一批零件，师傅单独加工需要4天完成，徒弟单独修需要6天完成．如果师徒两人一起加工，几天可以加工完成这批零件？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/4) + (1/6)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">1 / (5/12)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>