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NDA 2025
Exam
NDA
Year
2025
Subject
Mathematics
Chapter
Probability

NDA 2025 · Mathematics · Probability

Consider the following for the two (02) items that follow: A...

Consider the following for the two (02) items that follow:
A committee of 6 members is formed from a group of 7 gentlemen and 4 ladies.

What is the probability that the committee includes exactly 3 gentlemen?

Options

  1. A1033\dfrac{10}{33}
  2. B3077\dfrac{30}{77}
  3. C100231\dfrac{100}{231}
  4. D511\dfrac{5}{11}

Correct answer

A. 1033\dfrac{10}{33}

Step-by-step solution

Total number of people = 7+4=117 + 4 = 11

Total number of ways to select a committee of 66 members = 11C6^{11}C_{6}

To form a committee of 66 members with exactly 33 gentlemen, the remaining 33 members must be ladies.

Number of ways to select exactly 33 gentlemen and 33 ladies = 7C3×4C3^{7}C_{3} \times ^{4}C_{3}

Required probability = 7C3×4C311C6\dfrac{^{7}C_{3} \times ^{4}C_{3}}{^{11}C_{6}}

11C6=11×10×9×8×7×66×5×4×3×2×1=462^{11}C_{6} = \dfrac{11 \times 10 \times 9 \times 8 \times 7 \times 6}{6 \times 5 \times 4 \times 3 \times 2 \times 1} = 462

7C3=7×6×53×2×1=35^{7}C_{3} = \dfrac{7 \times 6 \times 5}{3 \times 2 \times 1} = 35

4C3=4^{4}C_{3} = 4

Required probability = 35×4462=140462=1033\dfrac{35 \times 4}{462} = \dfrac{140}{462} = \dfrac{10}{33}

Answer: 1033\dfrac{10}{33}
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