`A = 1/(1 . 2 . 3) + 1/(2 . 3 . 4) + (1/(3 . 4 . 5) + ... + 1/(98 . 99 . 100))`
`A = 1/2 . 2 . (1/(1 . 2 . 3) + 1/(2 . 3 . 4) + (1/(3 . 4 . 5) + ... + 1/(98 . 99 . 100))`
`A = 1/2 . (2 . 1/(1 . 2 . 3) + 1/(2 . 3 . 4) + (1/(3 . 4 . 5) + ... + 1/(98 . 99 . 100))`
`A = 1/2 . (2/(1 . 2 . 3) + 2/(2 . 3 . 4) + 2/(3 . 4 . 5) + ... + 2/(98 . 99 . 100))`
`A = 1/2 . (1/(1 . 2) - 1/(2 . 3) + 1/(2 . 3) - 1/(3 . 4) + ... + 1/(98 . 99) - 1/(99 . 100))`
`A = 1/2 . (1/(1 . 2) - 1/(99 . 100))`
`A = 1/2 . (1/2 - 1/(99 . 100))`
`A = 1/(2 . 2) - 1/(2 . 99 . 100)`
`A = 1/4 - 1/19800`
`A = 4949/19800`
