Uncle Wang set off from the county seat to Wangzhuang to deliver fertilizers. It took 3 hours to go and 4 hours to return, and the speed of going was 40 km/h. How many kilometers per hour did you travel on average when returning the same way?
王叔叔从县城出发去王庄送化肥．去的时候用了3小时，返回用了4小时，去的速度是40千米/时．原路返回时平均每小时行多少千米？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">40 * (3/4)</gadget>
<output>30</output>

<result>30</result>