The car goes up the mountain at a speed of 40 kilometers per hour. After driving for 5 hours, it only takes 4 hours to go down the mountain by the same road. How many kilometers per hour does the car go down the mountain?
汽车上山速度为每小时40千米，行了5小时，按原路下山只用了4小时，汽车下山每小时行多少千米？
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">40 * (5/4)</gadget>
<output>50</output>

<result>50</result>