For a pile of coal, (1/5) of the total is used for the first time, (2/5) tons are used for the second time, and (3/4) of the total is used for the two times. How many tons does this pile of coal weigh?
一堆煤，第一次用去总数的(1/5)，第二次用去(2/5)吨，两次共用去总数的(3/4)，这堆煤重多少吨？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">(3/4) - (1/5)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">(2/5) / (11/20)</gadget>
<output>8/11 = around 0.727273</output>

<result>8/11 = around 0.727273</result>