A student goes to school every day through three sections of uphill, flat road, and downhill, and the lengths of these three sections are equal; 3 meters per second, and the speed of cycling downhill is 4 meters per second, then what is the average speed of the three sections of the road in meters per second?
一同学每天的上学路上要经过上坡、平路、下坡三段路，并且这三段路的长度相等；如果他骑车上坡的速度是每秒2米，骑平路的速度是每秒3米，骑车下坡的速度是每秒4米，那么他走这三段路的平均速度是每秒多少米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/2) + (1/3) + (1/4)</gadget>
<output>13/12 = around 1.083333</output>

<gadget id="calculator">3 / (13/12)</gadget>
<output>36/13 = around 2.769231</output>

<result>36/13 = around 2.769231</result>