Place A is 10 kilometers away from place B. Xiaoming rides a bicycle from place A to place B and back again. The speed of cycling is 20 kilometers per hour when he goes there, and the speed of cycling when he comes back is the same speed as when he went there (3/5) , Find the average speed of the round trip?
甲地距乙地10千米，小明骑自行车从甲地到乙地往返一次，去时骑车的速度是每小时20千米，回来时骑车的速度是去时速度的(3/5)，求往返全程的平均速度？
<gadget id="calculator">10 / 20</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(1/2) * (3/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(3/10) + (1/2)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">10 / (4/5)</gadget>
<output>25/2 = around 12.5</output>

<result>25/2 = around 12.5</result>