During the "June 1st" Children's Day, the teachers of the art group organized a face painting activity. There are 9 classes in the fifth grade, with an average of 4 students in each class to paint faces, and it took a total of 72 minutes. How many minutes does it take on average to draw a face?
"六一"儿童节期间，美术组的老师们组织了画脸活动．五年级有9个班，平均每个班有4个同学去画脸，一共花了72分钟．平均画一张脸需要多少分钟．
<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<gadget id="calculator">72 / 36</gadget>
<output>2</output>

<result>2</result>