The age distribution of the students in Class 4 and Class 2 is as follows: 3 students are 13 years old, 15 students are 12 years old, 11 students are 11 years old, and 21 students are 10 years old. What is the average age of this class?
四2班学生年龄分布的情况是：13岁的有3人，12岁的有15人，11岁的有11人，10岁的有21人．这个班的平均年龄是多少岁？
<gadget id="calculator">13 * 3</gadget>
<output>39</output>

<gadget id="calculator">12 * 15</gadget>
<output>180</output>

<gadget id="calculator">11 * 11</gadget>
<output>121</output>

<gadget id="calculator">10 * 21</gadget>
<output>210</output>

<gadget id="calculator">39 + 180 + 121 + 210</gadget>
<output>550</output>

<gadget id="calculator">3 + 15 + 11 + 21</gadget>
<output>50</output>

<gadget id="calculator">550 / 50</gadget>
<output>11</output>

<result>11</result>