A certain factory needs to produce 6,000 mobile phones, and 2,800 have been produced in the first 7 days. According to this production speed, how many days will it take to produce these mobile phones in total? (Solve with ratio)
某厂要生产6000只手机，前7天已经生产了2800只，照这样的生产速度，这些手机一共要生产多少天？(用比例解)
<gadget id="calculator">2_800 / 7</gadget>
<output>400</output>

<gadget id="calculator">6_000 / 400</gadget>
<output>15</output>

<result>15</result>