MathDB
Putnam 1965 B5

Source:

September 28, 2020
Putnam

Problem Statement

Consider collections of unordered pairs of VV different objects aa, bb, cc, …\ldots, kk. Three pairs such as abab, bcbc, abab are said to form a triangle. Prove that, if 4E≤V24E\leq V^2, it is possible to choose EE pairs so that no triangle is formed.
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