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# Pre-RMO 2014/8

Let $$S$$ be the set of real numbers with mean $$M$$. If the means of the set $$S \cup \{ 15\}$$ and $$S \cup \{ 15, 1\}$$ are $$M + 2$$ and $$M + 1$$ respectively, then how many elements does $$S$$ have?

This note is part of the set Pre-RMO 2014

Note by Pranshu Gaba
2 years ago

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Answer is 4. · 2 years ago

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4 · 1 year, 5 months ago