The Xinxing store has newly shipped 9 boxes of pens, 20 in each box, and they are all sold out in 6 days. How many pens are sold on average per day?
新星商店新运进9盒钢笔，每盒20支，6天就全部卖完，平均每天卖多少支钢笔？
<gadget id="calculator">9 / 6</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">20 * (3/2)</gadget>
<output>30</output>

<result>30</result>