A pile of coal, if (1/5) of this pile of coal is transported away every day, how many days can it be transported.
一堆煤，每天运走这堆煤的(1/5)，多少天可运完．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<result>5</result>