In how many ways can 8 persons be arranged in a row such that there are always 2 person between A&B?
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Let the arrangement be
A,x,y,B,1,2,3,4
Consider A,x,y,B as one let Z
Z,1,2,3,4
No. Of ways = 5! = 120
Now x,y can be chosen in = 6C2
= 6!/4!*2! = 6*5/2 = 15
And x,y can be arranged in = 2!
A,B can be arranged in = 2!
No. Of total combination = 120*15*2*2
= 7200 ways ans
A,x,y,B,1,2,3,4
Consider A,x,y,B as one let Z
Z,1,2,3,4
No. Of ways = 5! = 120
Now x,y can be chosen in = 6C2
= 6!/4!*2! = 6*5/2 = 15
And x,y can be arranged in = 2!
A,B can be arranged in = 2!
No. Of total combination = 120*15*2*2
= 7200 ways ans
neosingh:
It's a difficult one, I am not sure if my ans is correct.
Wrong
6p2 will be used and 2! For z we can't do them together
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