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The Smith family has 4 sons and 3 daughters. In how many ways can they be seated in a row of 7 chairs such that at least 2 boys are next to each other?

 Apr 21, 2018

Best Answer 

 #1
avatar+4286 
+2

The total number of ways of seating \(7\) people is \(7!\)
The only disallowed seating arrangement is alternate boy-girl, \(\texttt{BGBGBGB}.\)  There are \(4!\) ways to seat the boys and \(3!\) ways to seat the girls. So the number of disallowed seating arrangements is \(4! \times 3!\)
The final answer is \(7! - 4! \times 3! = 5040-24\times 6=5040-144=4896\)

.
 Apr 21, 2018
 #1
avatar+4286 
+2
Best Answer

The total number of ways of seating \(7\) people is \(7!\)
The only disallowed seating arrangement is alternate boy-girl, \(\texttt{BGBGBGB}.\)  There are \(4!\) ways to seat the boys and \(3!\) ways to seat the girls. So the number of disallowed seating arrangements is \(4! \times 3!\)
The final answer is \(7! - 4! \times 3! = 5040-24\times 6=5040-144=4896\)

tertre Apr 21, 2018

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