There are 2,400 parts in a batch, and Master Li completed 40% in 3 days. According to this calculation, how many days will it take to complete this batch of parts?
一批零件有2400个，李师傅3天完成了40%，照这样计算，完成这批零件需要多少天？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / (2/5)</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>