A person goes up the mountain at a speed and goes down the mountain at a speed of 2a, what is his average speed a
某人上山速度为a，沿原路下山速度为2a，那么他的平均速度为多少a
<gadget id="calculator">4 / 3</gadget>
<output>4/3 = around 1.333333</output>

<result>4/3 = around 1.333333</result>