A pile of coal, (1/2) of the total number is transported away for the first time, and the remaining (1/2) is transported away for the second time, how much of the total number is left.
一堆煤，第-次运走总数的(1/2)，第二次运走剩下的(1/2)，还剩下总数的多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * (1/2)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>