The number of boys accounts for 5/9 of the whole class, and the number of girls is equal to the number of boys.
男生人数占全班人数的(5/9)，女生人数就相当于男生人数的多少．
<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">1 - (5/9)</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">(4/9) / (5/9)</gadget>
<output>4/5 = around 0.8</output>

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