A is (1/5) of B, C is (1/4) of B, and A is how much of C.
A是B的(1/5)，C是B的(1/4)，A是C的多少．
<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>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>