Xiao Ming’s speed from the bottom of the mountain to the top of the mountain is 3 kilometers per hour, and the speed from the top of the mountain to the bottom of the mountain is 5 kilometers per hour, so what is the average speed of Xiao Ming’s round trip from the bottom of the mountain to the top of the mountain in kilometers per hour
小明从山下走到山顶的速度是3千米/小时，从山顶返回山下的速度是5千米/小时，那么小明从山下到山顶往返的平均速度是多少千米/小时
<gadget id="calculator">1 * 2</gadget>
<output>2</output>

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

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

<gadget id="calculator">(1/3) + (1/5)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">2 / (8/15)</gadget>
<output>15/4 = around 3.75</output>

<result>15/4 = around 3.75</result>