There are 6 classes in the third and fourth grades of Dongpo Primary School, with an average of 45 students in each class of the third grade and 55 students in each class of the fourth grade. How many people are there in the third and fourth grades?
东坡小学三年级和四年级各有6个班，三年级平均每班有45人，四年级平均每班有55人．三、四年级一共有多少人？
<gadget id="calculator">6 * 45</gadget>
<output>270</output>

<gadget id="calculator">6 * 55</gadget>
<output>330</output>

<gadget id="calculator">270 + 330</gadget>
<output>600</output>

<result>600</result>