The number of boys is girls (4/5), then girls account for the whole class ((())/(())).
男生人数是女生的(4/5)，则女生占全班的((())/(()))．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<result>5/9 = around 0.555556</result>