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5

Part of 2011 Northern Summer Camp Of Mathematics

Problems(1)

Groups of scientists [Vietnam Northern Camp, 2011 - P5]

Source:

8/15/2011
In a meeting, there are 20112011 scientists attending. We know that, every scientist know at least 15091509 other ones. Prove that a group of five scientists can be formed so that each one in this group knows 44 people in his group.
induction