Uncle Zhang rides a bicycle across an overpass. The speed of the bridge is 8 kilometers per hour, and the speed of the bridge is 12 kilometers per hour. Moreover, the distance traveled by the bridge and the bridge are equal, and there is no pause in the middle. What is the average speed of Uncle Zhang cycling across the bridge?
张叔叔骑自行车过一道立交桥，上桥速度是每小时8千米，下桥速度是每小时12千米，而且上桥与下桥所经过的路程相等，中间也没有停顿．张叔叔骑车过这座桥的平均速度是多少？
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/8) + (1/12)</gadget>
<output>5/24 = around 0.208333</output>

<gadget id="calculator">2 / (5/24)</gadget>
<output>48/5 = around 9.6</output>

<result>48/5 = around 9.6</result>