The distance between A and B is 600 kilometers. Xiao Wang drove from A to B, and returned the same way after finishing his work. It is known to travel 40 kilometers per hour when going, and travel 60 kilometers per hour when returning. What is the average speed of the car back and forth in kilometers per hour.
甲乙两地相距600千米，小王开车从甲地到乙地，办完事后原路返回．已知去时每小时行40千米，返回时每小时行60千米．汽车来回的平均速度是每小时多少千米．
<gadget id="calculator">600 * 2</gadget>
<output>1_200</output>

<gadget id="calculator">600 / 40</gadget>
<output>15</output>

<gadget id="calculator">600 / 60</gadget>
<output>10</output>

<gadget id="calculator">15 + 10</gadget>
<output>25</output>

<gadget id="calculator">1_200 / 25</gadget>
<output>48</output>

<result>48</result>