data/problems/235.yml
---
:id: 235
:name: An Arithmetic Geometric sequence
:url: https://projecteuler.net/problem=235
:content: "Given is the arithmetic-geometric sequence u(<var>k</var>) = (900-3<var>k</var>)<var>r</var><sup><var>k</var>-1</sup>.
\ \nLet s(<var>n</var>) = Σ<sub><var>k</var>=1...<var>n</var></sub>u(<var>k</var>).\n\nFind
the value of <var>r</var> for which s(5000) = -600,000,000,000.\n\nGive your answer
rounded to 12 places behind the decimal point.\n\n"