Li Peng went back and forth between his home and Changsha by car. He traveled an average of 60 kilometers per hour when he went from home to Changsha, and an average of 40 kilometers per hour when he returned home from Changsha. Find his average round-trip speed?
李鹏坐车往返于他家与长沙之间．他从家去长沙时平均每小时行60千米，从长沙返回家时平均每小时行40千米，求他往返的平均速度？
<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/60) + (1/40)</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">2 / (1/24)</gadget>
<output>48</output>

<gadget id="calculator">1 * 48</gadget>
<output>48</output>

<result>48</result>