The distance between A and B is 120km. It takes 10 hours to travel from A to B, and 6 hours to return to A. Calculate the average speed of the round trip between A and B.
甲乙两地相距120km，从甲地去乙地共用10h，返回甲地时用6h，求往返甲乙两地的平均速度．
<gadget id="calculator">10 + 6</gadget>
<output>16</output>

<gadget id="calculator">2 / 16</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">120 * (1/8)</gadget>
<output>15</output>

<result>15</result>