Intermediate
Discrete Mathematics & Math
Q79 / 100
What is the multiplicative inverse of 3 modulo 7?
Correct! Well done.
Incorrect.
The correct answer is B) 5
B
Correct Answer
5
Explanation
We need x such that 3x ≡ 1 (mod 7). Testing: 3·5 = 15 = 14+1 ≡ 1 (mod 7), so x = 5. The inverse exists because gcd(3,7) = 1; it can also be found via the Extended Euclidean Algorithm.
Progress
79/100