Browse · MATH Print → jmc number theory senior Problem Given that 33−1≡77(mod508), find 11−1(mod508) as a residue modulo 508. (Give an answer between 0 and 507, inclusive.) Solution — click to reveal Since 33−1≡77(mod508), 11−1≡(33⋅3−1)−1≡33−1⋅3≡77⋅3≡231(mod508). Final answer 231 ← Previous problem Next problem →