Xiao Ming walked for 4 hours and traveled 20 kilometers, and it took him just 1 hour to return along the original road by bicycle. What is Xiao Ming's average round-trip speed in kilometers per hour
小明步行4小时走了20千米的路程，骑自行车沿原路返回刚好用1小时．小明往返的平均速度是每小时多少千米
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

<result>8</result>