A machine factory originally planned to produce 40 machines per day, and the task can be completed in 20 days. If it is to be completed 4 days in advance, how many units should be completed per day? (Solution with proportional knowledge)
一个机器厂原计划每天生产40台机器，20天可以完成任务．如果要提前4天完成，每天要完成多少台？(用比例知识解)
<gadget id="calculator">40 * 20</gadget>
<output>800</output>

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

<gadget id="calculator">800 / 16</gadget>
<output>50</output>

<result>50</result>