Xiaohong travels from A to B by boat at a speed of 6 km/h, and then returns along the original road by boat at a speed of 12 km/h, then Xiaohong travels on average per hour during the round trip by boat How many kilometers.
小红乘船以6千米/时的速度从A到B，然后，又乘船以12千米/时的速度沿原路返回，那么小红在乘船往返的行程中，平均每小时行驶多少千米．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

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

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/6) + (1/12)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">2 / (1/4)</gadget>
<output>8</output>

<result>8</result>