The school organizes tree planting labor, with an average of 4 trees planted per person. There are 42 students in the first class and 38 students in the second class. How many trees are planted in the two classes?
学校组织植树劳动，平均每人植树4棵．一班有学生42人，二班有学生38人，两个班一共植树多少棵？
<gadget id="calculator">42 + 38</gadget>
<output>80</output>

<gadget id="calculator">80 * 4</gadget>
<output>320</output>

<result>320</result>