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NDA 1 2024 Maths, question 18

Topic: Algebra

Q18

What is the remainder when 21202^{120} is divided by 77 ?

  1. (a) 11Correct answer
  2. (b) 33
  3. (c) 55
  4. (d) 66

Solution.

Answer: (a) 11

  1. Since 2³=8≡1 modulo 7 and 120=3×40, we have 2¹²⁰=(2³)⁴⁰≡1.
  2. The remainder is 1.