X = 1, then 1/1 = 1.00
X = 2, then 1/2 = 0.50
X = 3, then 1/3 = 0.33
X = 4, then 1/4 = 0.25
X = 5, then 1/5 = 0.20
X = 6, then 1/6 = 0.17
X = 7, then 1/7 = 0.14
X = 8, then 1/8 = 0.12
X = 9, then 1/9 = 0.11
So, if X > 1/X 的十分位,then, X = 2.
If X = 3, 十分位 是 2, 不对