`#Mon`
`M=\frac{1}{2.15}+\frac{1}{15.3}+\frac{1}{3.21}+...+\frac{6}{87.90}`
`M=\frac{6}{12.15}+\frac{6}{15.18}+...+\frac{6}{87.90}`
`M=2(\frac{3}{12.15}+\frac{3}{15.18}+...+\frac{3}{87.90})`
`M=2(\frac{1}{12}-\frac{1}{15}+\frac{1}{15}-\frac{1}{18}+...+\frac{1}{87}-\frac{1}{90})`
`M=\2(\frac{1}{12}-\frac{1}{90})`
`M=\frac{13}{90}`