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NDA 2025
Exam
NDA
Year
2025
Subject
Mathematics
Chapter
Permutation and Combination

NDA 2025 · Mathematics · Permutation and Combination

For the following two (02) items: There are 8 points on a plane out...

For the following two (02) items:
There are 8 points on a plane out of which 4 points are collinear.

How many quadrilaterals can be formed by joining these points?

Options

  1. A7070
  2. B6969
  3. C5353
  4. DNone of the above

Correct answer

C. 5353

Step-by-step solution

Total number of points is 88.

Number of collinear points is 44.

Total number of ways to select 44 points from 88 points is ^{8}C_{4} = 70.<br><br>Aquadrilateralcannotbeformedif3.<br><br>A quadrilateral cannot be formed if 3 or 44 selected points are collinear.

Number of ways to select 44 collinear points is ^{4}C_{4} = 1.<br><br>Numberofwaystoselect3.<br><br>Number of ways to select 3 collinear points and 11 non-collinear point is ^{4}C_{3} \times ^{4}C_{1} = 4 \times 4 = 16.<br><br>Totalnumberofquadrilateralsthatcanbeformedis70−(1+16)=53.<br><br>Total number of quadrilaterals that can be formed is 70 - (1 + 16) = 53.

Answer: 5353
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