1.1+1.91+1.991+.+1.{99.9}1= (2-0.9)+ (2-0.09)+ (2-0.009)+.+ (2-0.{00.0}9 { }处为100个0=2*101-(0.9+0.09+...+0.{00.0}9)=202-0.99.9(为101个9)=201.{0...0}1 { }处为100个0