person rides a bicycle from A to B at a speed of 30 kilometers per hour, and returns at a speed of 15 kilometers per hour, what is the average speed of this person during the round trip?
某人骑自行车从甲地到乙地，去时以每小时30千米的速度前进，回来时以每小时15千米的速度返回，那么此人在往返过程中的平均速度是多少
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

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

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/30) + (1/15)</gadget>
<output>1/10 = around 0.1</output>

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

<result>20</result>