A car drives in a mountainous area. It takes 3 hours to go up the mountain, traveling an average of 30 kilometers per hour. It only takes 2 hours to go down the mountain and return the same way. Find the average speed of the car going up and down the mountain.
一辆汽车在山区行驶，上山用了3小时，平均每小时行30千米，下山原路返回，只用了2小时，求这辆汽车上山、下山的平均速度．
<gadget id="calculator">30 * 3 * 2</gadget>
<output>180</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">180 / 5</gadget>
<output>36</output>

<result>36</result>