There are 400 girls in the sixth grade, and 80% of the boys are girls. How many students are there in the sixth grade?
六年级有女生400人，男生是女生的80%，六年级共有学生多少人？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">400 * (4/5)</gadget>
<output>320</output>

<gadget id="calculator">320 + 400</gadget>
<output>720</output>

<result>720</result>