A batch of cement, used (4/9), the rest is how much used
一批水泥，用去(4/9)，剩下的是用去的多少
<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 - (4/9)</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">(5/9) / (4/9)</gadget>
<output>5/4 = around 1.25</output>

<result>5/4 = around 1.25</result>