To process a batch of parts, it is planned to process 40 parts per day, and it will be completed in 20 days. Actually, 10 more parts will be processed per day. How many days will it be completed in advance?
加工一批零件，计划每天加工40个，20天完成，实际每天多加工10个，实际提前多少天完成？
<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">20 / 50</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">40 * (2/5)</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<result>4</result>