The school library has newly purchased 25 sets of the same extra-curricular books, each set has 4 books, and the total cost is 1,000 yuan. How much is each extracurricular book?
学校图书室新进了25套同样的课外书，每套有4本，一共花1000元．每本课外书多少元？
<gadget id="calculator">25 * 4</gadget>
<output>100</output>

<gadget id="calculator">1_000 / 100</gadget>
<output>10</output>

<result>10</result>