When a pile of coal is transported, (1/5) of the total is transported on the first day, and (1/4) of the total is transported on the second day, what fraction of the coal is left unshipped?
运一堆煤，第一天运走总数的(1/5)，第二天运走总数的(1/4)，还剩几分之几没有运？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) + (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (9/20)</gadget>
<output>11/20 = around 0.55</output>

<result>11/20 = around 0.55</result>