The Central Primary School held a mathematics knowledge competition. There were 4 classes in each of the fifth and sixth grades. Each class selected 10 students to participate. How many people participated in total?
中心小学举行数学知识竞赛，五六年级各有4个班，每个班选10人参加，一共有多少人参加？
<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">40 + 40</gadget>
<output>80</output>

<result>80</result>