A ship travels 30 kilometers per hour from A to B for a total of 8 hours, and then returns on the same route. When returning, it sails 60 kilometers per hour. Find the average speed of the ship in kilometers/hour Hour.
一艘轮船从甲地到乙地每小时航行30千米，一共走了8小时，然后按原路返回，返回时每小时航行60千米，求这艘轮船往返的平均速度是多少千米/小时．
<gadget id="calculator">8 / 60</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">30 * (2/15)</gadget>
<output>4</output>

<gadget id="calculator">4 + 8</gadget>
<output>12</output>

<gadget id="calculator">2 / 12</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">30 * 8 * (1/6)</gadget>
<output>40</output>

<result>40</result>