Students from 4 classes in the third grade participated in the rope skipping competition, a total of 120 people. If the number of students in each class is equal and each class is divided into 2 groups, how many people are there on average in each group?
三年级4个班的同学参加跳绳比赛，一共有120人．如果各班人数相等，每班分2组，平均每组有多少人？
<gadget id="calculator">120 / 4 / 2</gadget>
<output>15</output>

<result>15</result>