Uncle Zhang drove to the fertilizer store at a speed of 80 km/h. It took 3 hours to go there. Now Uncle Zhang is going to transport the fertilizer home from the store. It took 4 hours to return from the original road. The average speed when returning is How many?
张叔叔以80千米/时的速度开车去化肥商店，去的时候用了3小时，现在张叔叔要将化肥从商店运回家，原路返回时用了4小时，返回时的平均速度是多少？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">80 * (3/4)</gadget>
<output>60</output>

<result>60</result>