Tomorrow, when I go to Yuelu Mountain on May Day, the speed of going up the mountain is 20 meters per minute, and the speed of going back down the mountain is 30 meters per minute. What is the average speed of him going to and from Yuelu Mountain this time?
明明五一节去岳麓山，上山的速度是每分钟20米，下山按原路返回，速度是每分钟30米，求他这次往返岳麓山的平均速度是多少米．
<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>