The students went to plant trees. There are 3 classes in the third grade, and 45 trees are planted in each class. The number of trees planted in the fourth grade is twice the total number of the third grade. How many trees did the fourth grade plant?
同学们去植树．三年级3个班，每班种45棵，四年级种的棵数是三年级总数的2倍．四年级种了多少棵？
<gadget id="calculator">45 * 3 * 2</gadget>
<output>270</output>

<result>270</result>