The sportswear factory signed a production contract with the school for 2,400 sets of school uniforms, 20% of which were completed in the first 3 days. According to this calculation, how many days will it take to complete this task?
运动服厂与学校签订了2400套校服的生产合同，前3天完成了20%．照这样计算，完成这项任务一共要用多少天？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / (1/5)</gadget>
<output>15</output>

<result>15</result>