If you go back and forth on the same slope, the uphill speed is 5m/s, and the downhill speed is 7m/s, what is the average speed of one round trip in meters per second?
若在同一斜坡上往返，上坡速度为5m/s，下坡速度为7m/s，则往返一次的平均速度是多少米/秒．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/5) + (1/7)</gadget>
<output>12/35 = around 0.342857</output>

<gadget id="calculator">2 / (12/35)</gadget>
<output>35/6 = around 5.833333</output>

<result>35/6 = around 5.833333</result>