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NDA 2026
Exam
NDA
Year
2026
Subject
Mathematics
Chapter
Permutation and Combination

NDA 2026 · Mathematics · Permutation and Combination

What is the maximum number of points of intersection of 5 circles ?

What is the maximum number of points of intersection of 55 circles ?

Options

  1. A1010
  2. B1515
  3. C2020
  4. D2525

Correct answer

C. 2020

Step-by-step solution

Two circles can intersect at a maximum of 22 distinct points.

To find the maximum number of points of intersection of 55 circles, we select any 22 circles from the given 55 circles and multiply the number of pairs by 22.

The number of ways to select 22 circles from 55 is 5C2^{5}C_{2}.

Maximum number of points of intersection =2×5C2= 2 \times ^{5}C_{2}

=2×5×42×1= 2 \times \dfrac{5 \times 4}{2 \times 1}

=20= 20

Answer: 2020
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