An electrical appliance factory originally planned to produce 4,200 refrigerators in 21 days. The actual daily production of 210 units, the actual completion of the task a few days earlier than the original plan?
一个电器厂原计划21天生产电冰箱4200台．实际每天生产210台，实际比原计划提前几天完成任务？
<gadget id="calculator">4_200 / 210</gadget>
<output>20</output>

<gadget id="calculator">21 - 20</gadget>
<output>1</output>

<result>1</result>