For a pile of coal, 1/3 of the total amount is used for the first time, and the remaining 30% is used for the second time, and how much of the total amount is used for the second time.
一堆煤，第一次用去总数的(1/3)，第二次用了剩下的30%，第二次用去总数的多少．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/3) * (3/10)</gadget>
<output>1/5 = around 0.2</output>

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