Yongxin Cement Factory produces a batch of cement, originally planned to produce 120 tons per day, and can complete the task on time. In fact, an extra 30 tons was produced every day, and the task was completed in only 24 days. How many days was originally planned to complete the production task? (Solve with ratio)
永新水泥厂生产一批水泥，原计划每天生产120吨，可以按时完成任务．实际每天多生产30吨，结果只用24天就完成了任务．原计划完成生产任务需要多少天？(用比例解)
<gadget id="calculator">120 * 24</gadget>
<output>2_880</output>

<gadget id="calculator">30 * 24</gadget>
<output>720</output>

<gadget id="calculator">2_880 + 720</gadget>
<output>3_600</output>

<gadget id="calculator">3_600 / 120</gadget>
<output>30</output>

<result>30</result>