A=1/1*3+1/3*5+1/5*7+.....+1/99*101
A=1/3*(1-1/3+1/3-1/5+1/5-1/7+.......+1/99-1/101)
A=1/3*(1-1/101)
A=1/3*100/101
A=300/301
\(A=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{99.101}\)
\(A=\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\)
\(A=\frac{1}{1}-\frac{1}{101}=\frac{101}{101}-\frac{1}{101}=\frac{100}{101}\)