pile of coal is 80 tons, which is less than that of pile B (1/5), so how many tons of coal is pile B?
甲堆煤是80吨，比乙堆煤少(1/5)，则乙堆煤是多少吨．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">80 / (4/5)</gadget>
<output>100</output>

<result>100</result>