A pile of coal weighs (4/5) tons, and if (1/5) ton is used, what fraction of the pile of coal is used?
一堆煤重(4/5)吨，用去(1/5)吨，用去这堆煤的几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/5) / (4/5)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>