Four classes of students in the fourth and fifth grades of Experimental Primary School participated in the "Love My Hometown, Green Hometown" activity. 45 trees are planted in each class of the fifth grade, and 35 trees are planted in each class of the fourth grade. How many trees did the two grades plant in total?
实验小学四、五年级各有4个班的学生参加了"爱我家乡，绿化家乡"活动．五年级每班植树45棵，四年级每班植树35棵．两个年级一共植树多少棵？
<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">35 * 4</gadget>
<output>140</output>

<gadget id="calculator">180 + 140</gadget>
<output>320</output>

<result>320</result>