On Sunday, Xiaohua went to climb a mountain, going up the mountain at 2 kilometers per hour, and returning down the mountain along the same road at 3 kilometers per hour. What is the average speed of Xiaohua back and forth in kilometers per hour?
星期天，小华去爬山，上山每小时2千米，下山沿原路返回，每小时3千米，小华来回的平均速度是每小时多少千米．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/2) + (1/3)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">2 / (5/6)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>