To process a batch of parts, A alone can complete it in 4 hours, and B alone can complete it in 6 hours. A and B cooperate to complete ((())/(())) of this batch of parts every hour.
加工一批零件，甲单独做4小时完成，乙单独做6小时完成．甲、乙合做，每小时完成这批零件的((())/(()))．
<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>

<result>5/12 = around 0.416667</result>