Xiao Wang goes to school by bicycle and travels 18 kilometers per hour from home to school, and 12 kilometers per hour from school to home. What is the average speed of Xiao Wang to and from school in kilometers per hour?
小王上学骑车从家到学校每小时行18千米，从学校回家每小时行12千米，那么小王往返学校的平均速度是多少千米/小时．
<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

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

<gadget id="calculator">(1/18) + (1/12)</gadget>
<output>5/36 = around 0.138889</output>

<gadget id="calculator">2 / (5/36)</gadget>
<output>72/5 = around 14.4</output>

<gadget id="calculator">1 * (72/5)</gadget>
<output>72/5 = around 14.4</output>

<result>72/5 = around 14.4</result>