The production of one batch was originally planned to be completed in 18 days, but the actual production was 600 per day, which shortened the time by 6 days. How many parts were originally planned to be produced per day?
生产一批件，原计划18天完成，实际每天生产600个，这样时间缩短了6天．原计划每天生产多少个零件？
<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">12 / 18</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">600 * (2/3)</gadget>
<output>400</output>

<result>400</result>