A truck departs from A, fully loaded with goods, travels to B at a speed of 40 kilometers per hour, and returns empty, traveling 60 kilometers per hour. Find the average speed of the truck in kilometers per hour during this round trip.
一辆货车从甲地出发，满载货物以每小时40千米的速度前往乙地，到达后空车返回，每小时行60千米．求这辆货车在这次往返行程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 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / 60</gadget>
<output>1/60 = around 0.016667</output>

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

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

<result>48</result>