Dongdong went from home to grandma’s house by car. The average speed was 45 km/h, and it took 5 hours. It took 3 hours to return by the original road. What was the average speed of Dongdong’s car when he returned?
东东乘车从家去外婆家，去时平均速度是45千米/时，共用5小时，原路返回时用了3小时，东东返回时乘的这辆车的平均速度是多少？
<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">45 * (5/3)</gadget>
<output>75</output>

<result>75</result>