Yulong Primary School has 12 classes with an average of 35 students per class, and Shiguanchong Primary School has 10 classes with an average of 42 students per class. How many people are there in the two primary schools?
雨龙小学有12个班，平均每班35人，石缸冲小学有10个班，平均每班42人．两个小学一共有多少人？
<gadget id="calculator">35 * 12</gadget>
<output>420</output>

<gadget id="calculator">42 * 10</gadget>
<output>420</output>

<gadget id="calculator">420 + 420</gadget>
<output>840</output>

<result>840</result>