In a mountaineering competition, Li Ming walked 50 meters per minute when going up the mountain, reached the top of the mountain in 36 minutes, and walked 75 meters per minute when going down the mountain by the same route. Find the average speed of Li Ming going up and down the mountain once.
在一次登山比赛中，李明上山时每分钟走50米，36分钟到达山顶，按原路下山时，每分钟走75米．求李明上山下山往返一次的平均速度．
<gadget id="calculator">36 / 75</gadget>
<output>12/25 = around 0.48</output>

<gadget id="calculator">50 * (12/25)</gadget>
<output>24</output>

<gadget id="calculator">36 + 24</gadget>
<output>60</output>

<gadget id="calculator">2 / 60</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">50 * 36 * (1/30)</gadget>
<output>60</output>

<result>60</result>