A truck departs from the county town to the provincial capital to buy goods. It takes 3 hours to go there at a speed of 60 km/h, and it takes 4 hours to return by the original road. How many kilometers per hour does it travel when returning?
一辆货车从县城出发去省城进货，去时的速度是60千米/小时，用了3小时，原路返回时用了4小时，返回时每小时行驶多少千米？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">60 * (3/4)</gadget>
<output>45</output>

<result>45</result>