There are four numbers, the average of the first two numbers is 9.0, and the average of the last two numbers is 9.4, what is the average of these four numbers?
有四个数，其中前两个数的平均数是9.0，后两个数的平均数是9.4，这四个数的平均数是多少？
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">9.4 * 2</gadget>
<output>18.8</output>

<gadget id="calculator">18 + 18.8</gadget>
<output>36.8</output>

<gadget id="calculator">36.8 / 4</gadget>
<output>9.2</output>

<result>9.2</result>