A motorcycle driver travels 60 kilometers at a speed of 20 kilometers per hour, and travels 30 kilometers per hour when he returns. What is the average speed of the round trip?
摩托车驾驶员，以每小时20千米的速度行了60千米，回来时每小时行30千米，问往返全程平均速度是多少？
<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<gadget id="calculator">60 / 20</gadget>
<output>3</output>

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

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

<gadget id="calculator">120 / 5</gadget>
<output>24</output>

<result>24</result>