processing group produced 500 parts in March, exceeding the original plan (1/4). How many parts were originally planned to be produced?
某加工组3月份生产零件500个，比原计划超产(1/4)，原计划生产多少个零件？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">500 / (5/4)</gadget>
<output>400</output>

<result>400</result>