For a pile of coal, (4/5) tons are used on the first day, and (1/5) of the first day is used on the second day. How many tons are used on the second day?
一堆煤，第一天用去(4/5)吨，第二天用去的是第一天的(1/5)，第二天用去多少吨？
<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>