motorcyclist travels for 3 hours at a speed of 20 km/h. Then, immediately return along the original road and travel 30 kilometers per hour. What is the average round trip speed of this motorcycle in kilometers per hour?
一个摩托车驾驶员以每小时20千米的速度行了3小时．然后，立即沿原路返回，每小时行30千米．这辆摩托车往返的平均速度是每小时多少千米？
<gadget id="calculator">3 / 30</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 * (1/10)</gadget>
<output>2</output>

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

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 * 3 * (2/5)</gadget>
<output>24</output>

<result>24</result>