The distance between A and B is 120 kilometers. A car travels from A to B at an average of 24 kilometers per hour, and from B to A at an average of 40 kilometers per hour. What is the average speed of the car going back and forth?
甲、乙两地相距120千米，一辆汽车从甲地开往乙地平均每小时行驶24千米，由乙地返回甲地平均每小时行驶40千米，求汽车往返的平均速度？
<gadget id="calculator">120 / 24</gadget>
<output>5</output>

<gadget id="calculator">120 / 40</gadget>
<output>3</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">120 * (1/4)</gadget>
<output>30</output>

<result>30</result>