A batch of goods is planned to transport 30 tons per day, and the task is completed on schedule. If the daily tonnage is increased to 50 tons, and the shipment is completed in 6 days, how many days earlier than the original plan can the task be completed? (Column comprehensive formula solution)
一批货物，计划每天运30吨，按期完成任务，如果每天运的吨数增加到50吨，6天运完，这样可以比原计划提前多少天完成任务？(列综合算式解答)
<gadget id="calculator">6 / 30</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">50 * (1/5)</gadget>
<output>10</output>

<gadget id="calculator">10 - 6</gadget>
<output>4</output>

<result>4</result>