The factory produces a batch of parts. It originally planned to produce 400 parts per day, but actually produced 25% more per day. It actually took 20 days to complete the task. How many days did it take to complete the plan? (Solve with ratio)
工厂生产一批零件，原计划每天生产400个，实际每天多生产25%，实际用了20天完成任务，计划用了多少天完成？(用比例解)
<gadget id="calculator">400 * 20</gadget>
<output>8_000</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">400 * 20 * (1/4)</gadget>
<output>2_000</output>

<gadget id="calculator">8_000 + 2_000</gadget>
<output>10_000</output>

<gadget id="calculator">10_000 / 400</gadget>
<output>25</output>

<result>25</result>