Wuhu Iron and Steel Works wants to produce a batch of steel products, and plans to produce 600 tons per day, which will be completed in 20 days. The actual production is 800 tons per day. How many days will it take to complete it less than planned?
芜湖钢铁厂要生产一批钢材，计划每天生产600吨，20天完成．实际每天生产800吨，实际比计划少用多少天完成？
<gadget id="calculator">20 / 800</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">600 * (1/40)</gadget>
<output>15</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<result>5</result>