The school has to select 180 people from the third, fourth and fifth grades to participate in the broadcasting exercise performance. Each grade has 4 classes. How many people are selected in each class to participate in the performance on average?
学校要从三、四、五年级中选出180人参加广播操表演，每个年级各有4个班，平均每班选多少人参加表演？
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">180 / 12</gadget>
<output>15</output>

<result>15</result>