The distance between A and B is 280 kilometers. It takes 4.5 hours for a car to travel from A to B, and it takes 1 hour longer to return than to go. What is the average speed of this car going back and forth?
甲、乙两地相距280千米，一汽车从甲地到乙地用了4.5小时，返回时比去时多用1小时，求这辆汽车往返的平均速度？
<gadget id="calculator">280 * 2</gadget>
<output>560</output>

<gadget id="calculator">4.5 + 1 + 4.5</gadget>
<output>10</output>

<gadget id="calculator">560 / 10</gadget>
<output>56</output>

<result>56</result>