The distance between A and B is 260 kilometers. It takes 5.5 hours for a truck to transport goods from A to B. When returning, it takes 1 hour less than when going back because the truck is empty. Find the average round-trip speed of this truck.
甲、乙两地相距260千米，一辆货车从甲地运货到乙地用了5.5小时，返回时因为空车比去时少用了1小时，求这辆车往返的平均速度．
<gadget id="calculator">5.5 - 1</gadget>
<output>4.5</output>

<gadget id="calculator">5.5 + 4.5</gadget>
<output>10</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">260 * (1/5)</gadget>
<output>52</output>

<result>52</result>