Yan Yuchao has twice as many extracurricular books as Qiu Yunrou. Yan Yuchao has 40 extracurricular books, how many books does Qiu Yunrou have?
严宇朝同学的课外书本数是邱云柔同学的2倍．严宇朝有40本课外书，邱云柔有多少本．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>