A pile of coal is 2,400 tons in total, and 40% of this pile of coal was transported in the first 3 days. According to this calculation, how many days will it take to transport the remaining coal?
一堆煤共2400吨，前3天运走了这堆煤的40%，照这样计算，剩下的煤还要多少天运完？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / (2/5)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">(15/2) - 3</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>