It took a truck 5 hours to go from the county town to the countryside, and the speed of the truck was 40 km/h. It only took 4 hours to return, how many kilometers per hour can you calculate on average when you return?
一辆货车从县城到乡下，去的时候用了5小时，车的速度40千米/小时．返回时只用了4小时，你能算出返回时平均每小时行多少千米？
<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">5 * 10</gadget>
<output>50</output>

<result>50</result>