There are 6 classes for the third and fourth grades in a certain school, with an average of 55 students in each class of the third grade and 45 students in each class of the fourth grade. How many people are there in the third and fourth grades?
某校三、四年级各有6个班，三年级平均每班55人，四年级平均每班45人．三四年级共有多少人？
<gadget id="calculator">55 * 6</gadget>
<output>330</output>

<gadget id="calculator">45 * 6</gadget>
<output>270</output>

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

<result>600</result>