The distance between A and B is 180 kilometers. A person rides a bicycle from A to B. It takes 5 hours to go there, and it takes 4 hours to speed up when he returns. How many kilometers per hour does he travel on average?
甲乙两地相距180千米，某人骑自行车，从甲地到乙地，去时用了5小时，回来时加快速度用了4小时，他往返一次平均每小时行多少千米？
<gadget id="calculator">180 * 2</gadget>
<output>360</output>

<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">360 / 9</gadget>
<output>40</output>

<result>40</result>