IMO Practice Test — Number Systems

6 Questions • 15 min • Olympiad level

15:00
Question 1 of 6 medium
By Euclid's division lemma, a positive integer a can be written as a = 3b + 5, where 5 is the remainder (so 5 < b). If a = 23, find b.
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Explanation: By Euclid's division lemma, $23 = 3b + 5$ with remainder $5$, so $3b = 18$ and $b = 6$. The remainder condition $5 < b$ holds since $5 < 6$, and indeed $23 = 6 \times 3 + 5$.