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MathNet 2009-part-01 — 175 problems (EN–VI) Question 82

Math Olympiad Vault · MathNet 2009-part-01 — 175 problems (EN–VI)

Question 82

Let $q = 2p+1$, $p, q \gt 0$ primes. Prove that there exists a multiple of $q$ whose digits sum in decimal base is positive and at most 3.