Sunshine Instrument Factory needs to produce 400 sets of teaching aids and plans to complete the task in 25 days, but actually makes 4 sets more than the original plan every day. How many days will it actually take to complete the original production task?
阳光仪器厂要制作400套教具，计划25天完成任务，实际每天比原计划多做4套，实际完成原生产任务要多少天？
<gadget id="calculator">400 / 25</gadget>
<output>16</output>

<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<gadget id="calculator">400 / 20</gadget>
<output>20</output>

<result>20</result>