A total of 72 people from the fourth, fifth and sixth grades of the school were selected to participate in the performance on Children's Day on June 1st. Each grade has 6 classes. How many people are selected in each class on average?
"六一"儿童节学校四、五、六年级共选出72人参加表演，每个年级各有6个班．平均每个班选多少人？
<gadget id="calculator">3 * 6</gadget>
<output>18</output>

<gadget id="calculator">72 / 18</gadget>
<output>4</output>

<result>4</result>