What is the average of the eight numbers 9, 18, 19, 20, 21, 22, 23, and 24?
9，18，19，20，21，22，23，24这八个数的平均数是多少．
<gadget id="calculator">9 + 18 + 19 + 20 + 21 + 22 + 23 + 24</gadget>
<output>156</output>

<gadget id="calculator">156 / 8</gadget>
<output>39/2 = around 19.5</output>

<result>39/2 = around 19.5</result>