The students went to plant trees. The first class of the second grade planted 45 trees, the second class planted 20 trees, and the number of trees planted by the third grade was three times that of the second grade. How many trees did the third grade plant?
同学们去种树，二年级一班种了45棵，二班种了20棵，三年级种的棵数是二年级的3倍．三年级种了多少棵？
<gadget id="calculator">45 + 20</gadget>
<output>65</output>

<gadget id="calculator">65 * 3</gadget>
<output>195</output>

<result>195</result>