A batch of parts was completed by the master alone in 8 days, and by the apprentice in 10 days. Now they work together in 2 days, how much of this batch of parts can be completed.
一批零件，由师傅独做8天完成，由徒弟独做10天完成，现他俩合做2天，完成这批零件的多少．
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

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

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

<gadget id="calculator">(9/40) * 2</gadget>
<output>9/20 = around 0.45</output>

<result>9/20 = around 0.45</result>