The ratio of the number of girls to boys in grade six is 4:5, so how many girls account for the number of students in the whole grade?
六年级女生和男生人数的比是4：5，那么，女生占全年级学生人数的多少．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

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

<result>4/9 = around 0.444444</result>