A car travels from A to B in 5 hours, travels an average of 80 kilometers per hour, and only takes 3 hours to return. What is the average round-trip speed of this car?
一辆汽车从甲地开往乙地，用了5小时，平均每小时行80千米，返回时只用3小时，这辆汽车往返的平均速度是多少？
<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">80 * 5 * (1/4)</gadget>
<output>100</output>

<result>100</result>