Xiao Ming's speed from home to school is 5 km/h, and his speed from school to home after school is 4 km/h. What is the average speed of Xiaoming going to school and leaving school in kilometers per hour?
小明从家到学校的速度是5千米/时，放学从学校回家的速度是4千米/时．则小明上学、放学的平均速度是多少千米/时．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/5) + (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">2 / (9/20)</gadget>
<output>40/9 = around 4.444444</output>

<result>40/9 = around 4.444444</result>