Master Zhang drove to the county town to deliver goods. The distance from Master Zhang’s home to the county town was 150 kilometers. It took 2 hours to go there, and 3 hours to return by the same road. Find the average speed of Master Zhang’s car to and fro.
张师傅开车到县城运货物，张师傅的家到县城的距离是150千米，去时用了2小时，回来原路返回，用了3小时，求张师傅开车往返的平均速度．
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">150 * (2/5)</gadget>
<output>60</output>

<result>60</result>