A car travels from A to B in 8 hours at a speed of 40 km/h. It took only 4 hours to return. What was the speed of this car when it returned?
一辆汽车从甲地开往乙地，用了8小时，速度是40千米/时．返回时只用了4小时．这辆返回时的速度是多少？
<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>