It takes 5.5 hours for a correspondent to travel from point A to point B, and he travels 18 kilometers per hour; from point B to point A, he travels 22 kilometers per hour. What is the average speed of the correspondent traveling between the two places in kilometers per hour? ．
某通讯员从A地到B地，需要5.5小时，每小时行18千米；从B地返回A地，他每小时行22千米，该通讯员往返两地的平均速度是每小时行多少千米．
<gadget id="calculator">5.5 * 18 * 2</gadget>
<output>198</output>

<gadget id="calculator">18 / 22</gadget>
<output>9/11 = around 0.818182</output>

<gadget id="calculator">5.5 * (9/11)</gadget>
<output>4.5</output>

<gadget id="calculator">5.5 + 4.5</gadget>
<output>10</output>

<gadget id="calculator">198 / 10</gadget>
<output>99/5 = around 19.8</output>

<result>99/5 = around 19.8</result>