A pile of coal, burn it (2/5) every day, how many days can it be burned.
一堆煤，每天烧它的(2/5)，多少天可以烧完．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / (2/5)</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>