# Solution: 2016-7 Sum-free

For a set $$A \subset \mathbb{R}$$, let $$f(A)$$ be the size of the largest set $$B \subset A$$ such that $$(B+B) \cap B = \emptyset$$. For a positive integer $$n$$, let $$f(n) = \min_{0 \notin A, |A|=n} f(A)$$. Prove that $$f(n) \geq n/3$$.

The best solution was submitted by Kook, Yun Bum (국윤범, 수리과학과 2015학번). Congratulations!

Here is his solution of problem 2016-7.

Alternative solutions were submitted by 이종원 (수리과학과 2014학번, +3), 장기정 (수리과학과 2014학번, +3).

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