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If a, b are positive integers, where in the (modulo 7) with the multiplication operation, then inverse of 3 in the group is?

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If a, b are positive integers, where in the (modulo 7) with the multiplication operation, then inverse of 3 in the group is? Answer: 5

By checking the multiples of 3; (3\times 5=15\), and \(15\equiv 1\quad (\bmod 7)\). Therefore, the multiplicative inverse of 3 modulo 7 is 5.

Question context

This question is part of 📏 Arithmetic Aptitude within the broader 🧠 Aptitude Mastery subject and appears in the SPSC – Sindh Public Service Commission preparation collection. Reviewing the answer together with nearby questions helps reinforce the underlying concept and identify how it may appear in competitive exams.