`\frac{1}{120} - \frac{2}{30.33} - \frac{2}{33.36} - ... - \frac{2}{117.120}`
`= \frac{1}{120} - [ \frac{2}{3} ( \frac{2}{30.33} - \frac{3}{33.36} - ... - \frac{3}{117.120} )]`
`= \frac{1}{120} - [ \frac{2}{3} ( \frac{1}{30} - \frac{1}{33} - \frac{1}{33} - \frac{1}{36} - ... - \frac{1}{117} - \frac{1}{120} ) ]`
`= \frac{1}{120} - [ \frac{2}{3} ( \frac{1}{30} + \frac{1}{120} ) ]`
`= \frac{1}{120} - [ \frac{2}{3} . \frac{1}{24} ]`
`= \frac{1}{120} - \frac{2}{72}`
`= \frac{-168}{8640} = \frac{-7}{360}`
