A pile of coal weighs 2 tons. The pile of coal is used on the first day (1/5), the pile of coal is used on the second day (2/5), and the pile of coal is used on the third day (1/5 ), is this pile of coal used up? If not used up, how much is left?
一堆煤重2吨，第一天用去这堆煤的(1/5)，第二天用去这堆煤的(2/5)，第三天用去这堆煤的(1/5)，这堆煤用完了吗？如果没用完，还剩下几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/5) + (2/5) + (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>