There are 3 classes in the fourth grade, 4 classes in the fifth grade and 2 classes in the sixth grade. There are 48 students in each class of fourth grade, 45 students in each class of fifth grade, and 52 students in each class of sixth grade. How many people are there in the fourth and fifth grades?
牧民小学四年级有3个班，五年级有4个班，六年级有2个班．四年级每班48人，五年级每班45人，六年级每班52人．四、五年级一共有多少人？
<gadget id="calculator">48 * 3</gadget>
<output>144</output>

<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">144 + 180</gadget>
<output>324</output>

<result>324</result>