Teacher Wang bought 5 boxes of pens for 100 yuan, each box has 4 pens, how much is each pen?
王老师用100元钱买了5盒钢笔，每盒钢笔有4支，每支钢笔多少元？
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">100 / 20</gadget>
<output>5</output>

<result>5</result>