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Cono Sur Olympiad
1989 Cono Sur Olympiad
2
Finf the sum
Finf the sum
Source: Cono Sur Olymipiad, Urugay 1989, Problem#2
May 14, 2006
Problem Statement
Find the sum
1
+
11
+
111
+
⋯
+
111
…
111
⏟
n
digits
.
1+11+111+\cdots+\underbrace{111\ldots111}_{n\text{ digits}}.
1
+
11
+
111
+
⋯
+
n
digits
111
…
111
.
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