# [10,20] is a Problem!

**Algebra**Level 4

\[ \displaystyle S_n = \sum _{ r=1 }^{ n }{ \big[(r-10)(r-20) \big] } \]

Given the above function of \(S_n \), what does the summation below equal to?

\[\displaystyle \sum _{ r=1 }^{ 50 } \big|(r-10)(r-20)\big| \]