A pile of coal weighs (4/5) tons, and (1/5) is used on the first day. How many tons are used on the first day?
一堆煤重(4/5)吨，第一天用去了(1/5)，第一天用去多少吨？
<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>4/25 = around 0.16</output>

<result>4/25 = around 0.16</result>