The distance between A and B is 320 kilometers. It takes 6 hours for a car to drive from A to B, and 4 hours to return. What is the average speed of this car going back and forth in kilometers per hour?
甲乙两地相距320千米，一辆汽车从甲地开往乙地用了6小时，返回时用了4小时，这辆汽车往返的平均速度是每小时多少千米？
<gadget id="calculator">320 * 2</gadget>
<output>640</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">640 / 10</gadget>
<output>64</output>

<result>64</result>