Exercise · ZW-FERMAT-S-LITTLE-THEOREM-007 · ★★☆ Intermediate
Find the remainder of \(3^{50}\) when divided by \(7\).
Choose one option.
Show answer
- D. \(2\)
Explanation
Since \(7\) is prime, \(3^{6}\equiv 1\pmod 7\). Also \(50=6\cdot 8+2\), so \(3^{50}\equiv 3^{2}=9\equiv 2\pmod 7\). The option \(1\) is a typical error from ignoring the remainder of the exponent.
Review the concept: Fermat's little theorem
Fermat's little theorem states that if \(p\) is a prime number and \(a\) is an integer not divisible by \(p\), then \(a^{p-1}\equiv 1 \pmod{p}\). It is a basic tool for simplifying modular powers.
\[a^{p-1}\equiv 1 \pmod{p}, \quad p\nmid a\]
More practice problems: fermat's little theorem
- ZW-FERMAT-S-LITTLE-THEOREM-001 By Fermat's little theorem, what is a^p-1 congruent to modulo p when p is prime and pnmid a?
- ZW-FERMAT-S-LITTLE-THEOREM-002 What is the value of 3^6bmod 7?
- ZW-FERMAT-S-LITTLE-THEOREM-003 If p is prime, what condition on a is needed to use a^p-1≡ 1 pmodp?
- ZW-FERMAT-S-LITTLE-THEOREM-004 What is the remainder of 5^12 when divided by 13?
- ZW-FERMAT-S-LITTLE-THEOREM-005 If p=7 and a=2, what value does a^p-1bmod p take?
- ZW-FERMAT-S-LITTLE-THEOREM-006 Compute 2^100bmod 11.
- ZW-FERMAT-S-LITTLE-THEOREM-008 What is the value of 4^30bmod 13?
- ZW-FERMAT-S-LITTLE-THEOREM-009 Compute 6^17bmod 17.
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