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In sub - part (i) to (x) choose the corr...

In sub - part (i) to (x) choose the correct option and in sub - part (xi) to (xy), answer the questions as intructed .
Six boys and six girls sit in row rouldelary Probability that boys and girl sit alternately is :

A

`(1)/(462)`

B

`(1)/(264)`

C

`(1)/(426)`

D

None of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem of finding the probability that boys and girls sit alternately in a circular arrangement, we can follow these steps: ### Step 1: Understand the arrangement We have 6 boys and 6 girls, making a total of 12 individuals. Since we want them to sit alternately, we can either start with a boy or a girl. ### Step 2: Calculate the total arrangements In a circular arrangement, the total number of ways to arrange 12 individuals is given by \((n-1)!\) where \(n\) is the total number of individuals. Thus, the total arrangements are: \[ \text{Total arrangements} = (12 - 1)! = 11! \] ### Step 3: Calculate the favorable arrangements For the boys and girls to sit alternately, we can consider two cases: 1. Starting with a boy: The arrangement will be BGBGBGBGBGBG. 2. Starting with a girl: The arrangement will be GBGBGBGBGBG. In both cases, we can arrange the boys and girls independently. The number of ways to arrange 6 boys is \(6!\) and the number of ways to arrange 6 girls is also \(6!\). Thus, the favorable arrangements for each case are: \[ \text{Favorable arrangements for one case} = 6! \times 6! \] Since there are two cases (starting with a boy or starting with a girl), the total favorable arrangements are: \[ \text{Total favorable arrangements} = 2 \times (6! \times 6!) \] ### Step 4: Calculate the probability The probability \(P\) that boys and girls sit alternately is given by the ratio of favorable arrangements to total arrangements: \[ P = \frac{\text{Total favorable arrangements}}{\text{Total arrangements}} = \frac{2 \times (6! \times 6!)}{11!} \] ### Step 5: Simplify the probability We know that \(11! = 11 \times 10 \times 9 \times 8 \times 7 \times 6!\). Therefore, we can simplify: \[ P = \frac{2 \times (6! \times 6!)}{11 \times 10 \times 9 \times 8 \times 7 \times 6!} = \frac{2 \times 6!}{11 \times 10 \times 9 \times 8 \times 7} \] ### Step 6: Calculate \(6!\) Calculating \(6!\): \[ 6! = 720 \] ### Step 7: Substitute and calculate the final probability Substituting \(6!\) into the probability: \[ P = \frac{2 \times 720}{11 \times 10 \times 9 \times 8 \times 7} \] Calculating the denominator: \[ 11 \times 10 = 110, \quad 110 \times 9 = 990, \quad 990 \times 8 = 7920, \quad 7920 \times 7 = 55440 \] Thus, the probability becomes: \[ P = \frac{1440}{55440} = \frac{1}{38.5} \approx \frac{1}{462} \] ### Final Answer The probability that boys and girls sit alternately is: \[ \frac{1}{462} \]
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