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Suppose that n people are seated in a random manner in a row of n theatre seats. What is the probability that two particular people A and B will be seated next to each other?

Short Answer

Expert verified

The probability of two people A and B will be seated next to each other in the theatre is\(\frac{2}{n}\).

Step by step solution

01

Given information 

N people are seated randomly in a row with n seats.

02

Compute the favourable counts

The total number of ways of arranging n people into n seats is n!.

If A and B sit adjacent to each other, they are treated as a single object.

Therefore, the total number of ways of arranging n-1 objects will be\(\left( {n - 1} \right)!\).

Also, A and B can swap their places; therefore, there are 2! Ways of arranging the two people in a row.

Hence the number of possible arrangements is \(2! \times \left( {n - 1} \right)! = 2\left( {n - 1} \right)!\) .

03

Compute the probability

The probability that A and B are sitting next to each other in a n seat row is,

\(\begin{aligned}{}P\left( E \right) &= \frac{{2 \times \left( {n - 1} \right)!}}{{n!}}\\ &= \frac{{2\left( {n - 1} \right)!}}{{n\left( {n - 1} \right)!}}\\ &= \frac{2}{n}\end{aligned}\)

Thus, the required probability is \(\frac{2}{n}\).

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Most popular questions from this chapter

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