Ta có:
[tex]\frac{1}{101}<\frac{1}{99}[/tex]
[tex]\frac{1}{102}<\frac{1}{99}[/tex]
......................................................
[tex]\frac{1}{200}<\frac{1}{99}[/tex]
Cộng theo vế:
[tex]\frac{1}{101}+\frac{1}{102}+...+\frac{1}{200}<\frac{1}{99}+\frac{1}{99}+...+\frac{1}{99}=1[/tex]