If the ratio of boys to girls in a class is 4:5, what is the percentage of girls in the class?
某班男、女生人数比是4：5，则女生是全班总人数的多少．
<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>