A batch of parts can be completed in 8 days alone, and B can be completed in 10 days alone. Now the two work together to complete this batch of parts. A asks for a day off in the middle, how many days will it take to complete this batch of parts.
一批零件，甲独做8天完成，乙独做10天完成，现在由两人合作完成这批零件，中途甲请假一天，完成这批零件共用多少天．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) + (1/10)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">(9/10) / (9/40)</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>