A pile of coal was brought in from the cafeteria, 40% of which was used, leaving 3.6 tons. How many tons is this pile of coal?
食堂运来一堆煤，用去40%，还剩下3.6吨．这堆煤原有多少吨．
<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">3.6 / (3/5)</gadget>
<output>6</output>

<result>6</result>