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NDA 2024
Exam
NDA
Year
2024
Subject
Mathematics
Chapter
Permutation and Combination

NDA 2024 · Mathematics · Permutation and Combination

A man has 7 relatives ( 4 women and 3 men). His wife also has 7...

A man has 7 relatives ( 4 women and 3 men). His wife also has 7 relatives ( 3 women and 4 men). In how many ways can they invite 3 women and 3 men so that 3 of them are man's relatives and 3 of them are his wife's relatives?

Options

  1. A340
  2. B484
  3. C485
  4. D469

Correct answer

C. 485

Step-by-step solution

Total number of ways =4C3×4C3=4×4=16+3C1×4C2×4C2×3C1=18×18=324+3C3×4C0×4C0×3C3=1×1×1×1=1+3C2×4C1×4C1×3C2=12×12=144\begin{aligned} &={ }^4 \mathrm{C}_3 \times{ }^4 \mathrm{C}_3=4 \times 4=16 \\ &+{ }^3 \mathrm{C}_1 \times{ }^4 \mathrm{C}_2 \times{ }^4 \mathrm{C}_2 \times{ }^3 \mathrm{C}_1 \\ &=18 \times 18=324 \\ &+{ }^3 \mathrm{C}_3 \times{ }^4 \mathrm{C}_0 \times{ }^4 \mathrm{C}_0 \times{ }^3 \mathrm{C}_3 \\ &=1 \times 1 \times 1 \times 1=1 \\ &+{ }^3 \mathrm{C}_2 \times{ }^4 \mathrm{C}_1 \times{ }^4 \mathrm{C}_1 \times{ }^3 \mathrm{C}_2 \\ &=12 \times 12=144 \end{aligned} Hence, they can invite total no. of ways =16+324+1+144=485.=16+324+1+144=485 .
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