Students stand in line, boys and girls stand in 4 rows, 40 boys in each row, 60 girls in each row. How many fewer boys than girls?
同学们站队，男女生都站成4行，男生每行40人，女生每行60人．男生比女生少多少人？
<gadget id="calculator">60 - 40</gadget>
<output>20</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>