Wang Ming went to the county town to pick up goods, and the speed of the car was 40 km/h when he went there, and he drove for 5 hours. The speed of the car was 50 km/h when returning, how many hours did it take to return?
王明去县城拉货，去时汽车的速度为40千米/时，行驶了5小时．回来时汽车的速度为50千米/时，回来时用了几小时？
<gadget id="calculator">5 / 50</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">40 * (1/10)</gadget>
<output>4</output>

<result>4</result>