In (1/2), (2/3), (4/9) three numbers, add more to form a ratio.
在(1/2)、(2/3)、(4/9)三个数，再添上多少就可以组成比例．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">(2/3) / (4/9)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(1/2) * (3/2)</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>