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NDA 2023
Exam
NDA
Year
2023
Subject
Mathematics
Chapter
Probability

NDA 2023 · Mathematics · Probability

In a class, there are n students including the students P and Q....

In a class, there are n students including the students P and Q. What is the probability that P and Q sit together if seats are assigned randomly?

Options

  1. A1n\frac{1}{n}
  2. B2n\frac{2}{n}
  3. C4n\frac{4}{n}
  4. D12n\frac{1}{2 n}

Correct answer

B. 2n\frac{2}{n}

Step-by-step solution

The number of ways in which pp and qq seat together =(n−1)!×2=(\mathrm{n}-1)!\times 2 So, required Probability =2(n−1)!n!=2n=\frac{2(n-1)!}{n!}=\frac{2}{n}
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