There are 4 classes in the fourth grade of the school, with 45 students in each class, and a total of 720 trees are planted. How many trees are planted by each person on average?
学校四年级有4个班，每个班45人，共植树720棵，平均每人植树多少棵？
<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">720 / 180</gadget>
<output>4</output>

<result>4</result>