A pile of coal weighs (4/5) tons, and (1/5) tons are used up, how many tons should be multiplied?
一堆煤重(4/5)吨，用去了(1/5)吨，还乘多少吨？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(4/5) - (1/5)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>