In a mountaineering activity, when Xiao Li went up the mountain, he walked 50 meters per minute and reached the top of the mountain in 18 minutes. Then he went down the mountain the same way, walking 75 meters per minute. What is the average speed of Xiaoli going up and down the mountain?
在一次登山活动中，小李上山时，每分走50米，18分到达山顶．然后他按原路下山，每分走75米．小李上山、下山的平均速度是多少．
<gadget id="calculator">50 * 18 * 2</gadget>
<output>1_800</output>

<gadget id="calculator">50 * 18</gadget>
<output>900</output>

<gadget id="calculator">900 / 75</gadget>
<output>12</output>

<gadget id="calculator">18 + 12</gadget>
<output>30</output>

<gadget id="calculator">1_800 / 30</gadget>
<output>60</output>

<result>60</result>