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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. Ar Agarwal · 2 years ago

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@Ar Agarwal HOW ???????????????????? Rohit Nair · 1 year, 12 months ago

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ans is 4. Kishan Chaudhary · 1 year ago

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4 Sahil Nare · 1 year, 5 months ago

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the answer is 4 . equations are y/x=m y+15/x+1=m+2 y+16/x+2=m+1 where y is the sum of numbers and x is the number of elements. thus solving them , we get x=4 Ärnäv Mändäl · 1 year, 11 months ago

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