Yongfeng Agricultural Machinery Factory processes 2480 parts in one workshop. Originally, 100 pieces were processed per day, but after 20 days, it was changed to 120 pieces per day. How many days will it take to complete the task?
永丰农机厂一个车间加工2480个零件．原来每天加工100个，20天后，改为每天加工120个．要完成任务一共需要多少天？
<gadget id="calculator">100 * 20</gadget>
<output>2_000</output>

<gadget id="calculator">2_480 - 2_000</gadget>
<output>480</output>

<gadget id="calculator">480 / 120</gadget>
<output>4</output>

<gadget id="calculator">20 + 4</gadget>
<output>24</output>

<result>24</result>