Master Wang processed a batch of parts in June, and planned to process 45 parts every day for 20 days to complete the task. Due to other processing tasks, Master Wang actually processed 50 pieces a day. How many days did Master Wang actually spend on processing this batch of parts? (Solve using ratio method)
王师傅六月份加工一批零件，计划每天加工45个零件20天正好完成任务．由于又有其他加工任务，王师傅实际每天加工50个，加工这批零件王师傅实际用了多少天完成？(用比例方法解答)
<gadget id="calculator">45 * 20</gadget>
<output>900</output>

<gadget id="calculator">900 / 50</gadget>
<output>18</output>

<result>18</result>