A workshop needs to process 540 parts, 180 of which were processed in the first 2 days. According to this calculation, how many days are left to complete the task? (Solve with ratio)
某车间要加工540个零件，前2天加工了180个，照这样计算，剩下的还要几天才能完成任务？(用比例解)
<gadget id="calculator">540 - 180</gadget>
<output>360</output>

<gadget id="calculator">360 * 2</gadget>
<output>720</output>

<gadget id="calculator">720 / 180</gadget>
<output>4</output>

<result>4</result>