Master Li has to process 240 parts. 20% of the total was completed in the first 4 days. According to this calculation, how many days will it take Master Li to finish processing this batch of parts?
李师傅要加工240个零件．前4天完成了总数的20%，照这样计算，加工完这批零件，李师傅共要用多少天？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / 4</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>