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NDA 2021
Exam
NDA
Year
2021
Subject
Mathematics
Chapter
Permutation and Combination

NDA 2021 · Mathematics · Permutation and Combination

Suppose 20 distinct points are placed randomly on a circle. Which...

Suppose 20 distinct points are placed randomly on a circle. Which of the following statements is/are correct? 1. The number of straight lines that can be drawn by joining any two of these points is 380. 2. The number of triangles that can be drawn by joining any three of these points is 1140. Select the correct answer using the code given below.

Options

  1. A1 only
  2. B2 only
  3. CBoth 1 and 2
  4. DNeither 1 nor 2

Correct answer

B. 2 only

Step-by-step solution

Number of St lines =20C2=190={ }^{20} \mathrm{C}_2=190 Number of triangles =20C3=1140={ }^{20} \mathrm{C}_3=1140
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