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How many different ways can 2 students be seated in a r

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by nisagl750 » Sun Dec 16, 2012 6:37 am
varun289 wrote:How many different ways can 2 students be seated in a row of 4 desks, so that there is always at least one empty desk between the students?
A. 2
B. 3
C. 4
D. 6
E. 12
Let the two students be A and B

The possible arrangements are
A._.B._
_.A._.B
B._.A._
_.B._.A
A._._.B
B._._.A

IMO D

What is the OA?
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by Anurag@Gurome » Sun Dec 16, 2012 6:38 am
varun289 wrote:How many different ways can 2 students be seated in a row of 4 desks, so that there is always at least one empty desk between the students?
The possible scenarios are,
  • 1. They are occupying 1st and 3rd seat
    2. They are occupying 2nd and 4th seat
    3. They are occupying 1st and 4th seat
Hence, 3 ways.

As the two student can be arranged in two ways in each of the above possible scenarios, total number of ways are 2*3 = 6

The correct answer is D.
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