It took the courier 4 hours to deliver the courier from the county town to the countryside, with an average of 50 kilometers per hour, and an extra hour to return. How many kilometers per hour did you travel on average when returning the same way?
快递员从县城出发到乡下送快递，去的时候用了4小时，平均每小时行50千米，返回时多用1小时．原路返回时平均每小时行多少千米？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

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

<result>40</result>