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CUET
-- Applied Mathematics - Section B2
Numbers, Quantification and Numerical Applications
The least non-negative remainder when $3^{51}$ is divided by 7 is:
2
3
6
5
The correct answer is Option (3) → 6
$3^6=729.$
$729 \equiv 1 \pmod{7}.$
$3^{51}=(3^6)^8\cdot3^3.$
$3^{51}\equiv1^8\cdot27\pmod{7}.$
$27\equiv6\pmod{7}.$
$6.$