Class 31 students who participated in the tree planting were divided into 4 groups, each group had 9 people, and they planted 144 trees on Arbor Day. How many trees are planted per person on average?
三1班参加植树的同学分成4个小组，每个小组有9人，他们在植树节共植树144棵．平均每人植树多少棵？
<gadget id="calculator">4 * 9</gadget>
<output>36</output>

<gadget id="calculator">144 / 36</gadget>
<output>4</output>

<result>4</result>