The ratio of girls to boys in a school is 8:9. If there are 720 boys in the school, how many girls are there?
某校女生和男生人数的比是8：9．如果该校男生有720人，女生有多少人．
<gadget id="calculator">8 / 9</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">720 * (8/9)</gadget>
<output>640</output>

<result>640</result>