The average speed of Xiaoping going up the mountain is 20 meters per minute, and the average speed of going down the mountain along the original road is 30 meters per minute. What is the average speed of Xiaoping going up and down the mountain in meters per minute?
小平上山的平均速度是每分钟20米，下山沿原路返回，平均速度是每分钟30米，小平上、下山的平均速度是每分钟多少米．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

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

<gadget id="calculator">(1/20) + (1/30)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">2 / (1/12)</gadget>
<output>24</output>

<result>24</result>