MCQ
The remainder when ${5^{99}}$ is divided by $13$ is
  • A
    $6$
  • $8$
  • C
    $9$
  • D
    $10$

Answer

Correct option: B.
$8$
b
(b) ${5^{99}} = (5)\,{({5^2})^{49}} = 5{(25)^{49}} = 5{(26 - 1)^{49}}$

= $5 \times (26) \times ({\rm{Positive terms)--5,}}$ So when it is divided by $13$ it gives the remainder $-5$ or $(13 -5)$ $i.e.,$ $8$.

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