Xiao Liang's speed when going up the mountain is 2 kilometers per hour, and his speed when going down the mountain is 6 kilometers per hour. Then, what is his average speed in kilometers during the whole process of going up and down the mountain?
小亮上山时的速度是每小时走2千米，下山时的速度是每小时走6千米，那么，他在上、下山全过程中的平均速度是多少千米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/2) + (1/6)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">2 / (2/3)</gadget>
<output>3</output>

<result>3</result>