A road is 150 kilometers long. A car travels 30 kilometers per hour when going up the mountain, and 50 kilometers per hour when returning from the original road and going down the mountain. How many kilometers per hour does this car travel on average?
一条公路长150千米，一辆汽车上山时每小时行驶30千米，从原路返回下山时每小时行驶50千米，这辆汽车往返平均每小时行驶多少千米？
<gadget id="calculator">150 * 2</gadget>
<output>300</output>

<gadget id="calculator">150 / 30</gadget>
<output>5</output>

<gadget id="calculator">150 / 50</gadget>
<output>3</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">300 / 8</gadget>
<output>75/2 = around 37.5</output>

<result>75/2 = around 37.5</result>