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Difficulty: 4/102024 NMTC 2024 (Q32)

What is the remainder when is divided by ?

Options:

  • A.

    1

  • 3

  • C.

    9

  • D.

    12

Guide / Hint

Hint 1: Apply Fermat's Little Theorem to simplify the large exponent modulo 13.

Hint 2: Write as to reduce the problem to finding .

Hint 3: Calculate powers of 7 mod 13 progressively: .

Solution

Step 1 (Fermat's Little Theorem): Since 13 is prime and , Fermat's Little Theorem states:

Step 2 (Exponent Division): Divide the exponent 2024 by 12 to find the remainder:

Therefore:

Step 3 (Evaluate 7^8 mod 13):

Thus, the remainder when is divided by 13 is exactly .

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    2024 NMTC 2024 Q32 - Olympiad Math Olympiad Question | Leminno