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MathNet 2015-part-03 — 191 problems (EN–VI) Question 94

Math Olympiad Vault · MathNet 2015-part-03 — 191 problems (EN–VI)

Question 94

From a set of 11 square integers, show that one can choose 6 numbers $a^{2}, b^{2}, c^{2}, d^{2}, e^{2}, f^{2}$ such that
$$
a^{2}+b^{2}+c^{2} \equiv d^{2}+e^{2}+f^{2} \quad(\bmod 12)
$$