A pile of coal, after 40% of the total amount was used, was transported in 24 tons. The current tonnage is 5/7 of the original total amount. How many tons did this pile of coal have?
一堆煤，用去总数的40%后，又运进24吨，现在的吨数是原来总数的(5/7)，这堆煤原有多少吨？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(5/7) - (3/5)</gadget>
<output>4/35 = around 0.114286</output>

<gadget id="calculator">24 / (4/35)</gadget>
<output>210</output>

<result>210</result>