A car goes from place A to place B. The uphill road takes up 4/5 of the whole journey, and the downhill road takes up 1/5 of the whole journey. The uphill speed is 2 meters per second, and the downhill speed is 3 meters per second. This car What is the average speed in meters per second.
一辆车从甲地到乙地，其中上坡路占全程的(4/5)，下坡路占全程的(1/5)，上坡速度每秒2米，下坡速度每秒3米，这辆车的平均速度是每秒多少米．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) / 2</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(1/5) / 3</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(2/5) + (1/15)</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">1 / (7/15)</gadget>
<output>15/7 = around 2.142857</output>

<result>15/7 = around 2.142857</result>