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Seating - PS

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by karthikpandian19 » Tue Dec 06, 2011 12:12 am
In how many ways can Ann, Bea, Cam, Don, Ella and Fey be seated if Ann and Bea cannot be seated next to each other?

(A) 240 (B) 360(C) 480(D) 600(E) 720
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Source: — Problem Solving |

by Anurag@Gurome » Tue Dec 06, 2011 12:23 am
karthikpandian19 wrote:In how many ways can Ann, Bea, Cam, Don, Ella and Fey be seated if Ann and Bea cannot be seated next to each other?

(A) 240 (B) 360(C) 480(D) 600(E) 720
Total ways of seating 6 people = 6!
Consider Ann and Bea as one person, then number of ways of arranging 5 people = 5!
Number of ways of arranging Ann and Ben = 2!
Required number of ways of seating 6 people if Ann and Bea are not seated next to each other = 6! - 5!2! = 720 - 240 = 480

The correct answer is C.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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by dkolkin » Mon Dec 12, 2011 9:06 am
Dear Anurag, could you please explain why in this task do we take A and B as one person?
And what do 5!2! mean?

Thank you!
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