There are 320 boys in the sixth grade. The ratio of boys to girls is 8:7. How many girls are there?
六年级有男生320人，男生与女生人数的比是8：7，女生有多少人？
<gadget id="calculator">320 / 8</gadget>
<output>40</output>

<gadget id="calculator">40 * 7</gadget>
<output>280</output>

<result>280</result>