Someone walks around a square square. It is known that he walks 1 km per hour on the first side; 2 km per hour on the second side; 3 km per hour on the third side; 4 km per hour on the fourth side. So what is the average speed of this person walking in kilometers per hour?
某人沿着一个正方形的广场走一圈．已知他走的第一边每小时行1千米；走第二边每小时行2千米；走第三边每小时行3千米；走第四边每小时行4千米．那么这个人步行的平均数度是每小时多少千米．
<result>1.92</result>