The distance between A and B is 180km. It takes 2 hours for a car to travel from A to B, and it takes 3 hours to return due to traffic jam. Find the average speed of the car going back and forth.
甲、乙两地相柜180km，一辆汽车从甲地到乙地用了2小时，返回时由于堵车用了3小时，求这辆汽车往返的平均速度．
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">180 * (2/5)</gadget>
<output>72</output>

<result>72</result>