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MathNet 2024-part-01 — 168 problems (EN–VI) Question 127

Math Olympiad Vault · MathNet 2024-part-01 — 168 problems (EN–VI)

Question 127

There are 100 students in a summer camp, with exactly 2024 pairs of mutual friends. We need to divide them into 50 groups of 2 students each. Prove that:
1. It's possible to group them such that at most 20 groups contain mutual friends;
2. It's possible to group them such that at least 23 groups contain mutual friends;
3. It's possible to group them such that exactly 22 groups contain mutual friends.