A, B, and C work together to process a batch of parts. When the work is completed, the number of parts processed by A is twice that of B, and the number of parts processed by C is half of that of B. How much of this batch of parts does C complete.
甲、乙、丙三人共同加工一批零件，完工时甲加工的零件数是乙的2倍，丙加工的零件数是乙的一半，丙完成了这批零件的多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + 2 + (1/2)</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">(1/2) / (7/2)</gadget>
<output>1/7 = around 0.142857</output>

<result>1/7 = around 0.142857</result>