A children's clothing factory planned to produce 30,000 pieces of children's clothing in May, but 40% of the task was completed in the first 10 days. According to this calculation, how many days can this batch of tasks be completed in advance?
某童装厂五月份计划生产童装3万件，结果前10天就完成任务的40%，照这样计算，可提前几天完成这批任务？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">10 / (2/5)</gadget>
<output>25</output>

<gadget id="calculator">31 - 25</gadget>
<output>6</output>

<result>6</result>