combinatorics

Question

que- in how many way  can 7 girl are seated at a round table so that 2 particular girl are seprated ???

Comments

(7-1)! -(7-2)!

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something wrong ...

options are a-120 b-260 c-320 d-480 e-560

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Arrange 5 girls first in circle.

Circular permutation with n objects = (n-1)!

So it will take =4!=24 ways

Now we have 5 gaps between these 5 girls,arrange the remaining two girls in P(5,2)=20

Total ways = 24*20 =480

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thanks

Answer 1

@ Angkit Reframing you solution :
Total possible ways for 7 people : 6!
Total ways for 2 particular girls to sit next to each other with 5 other people : 5!

6!-5!*2!=5!(6-2)=5!*4=480 

Comments

got it .. :-) thnx saxena0612

Answer 2

Arrange 5 girls first in circle.

Circular permutation with n objects = (n-1)!

So it will take =4!=24 ways

Now we have 5 gaps between these 5 girls,arrange the remaining two girls in P(5,2)=20

Total ways = 24*20 =480

Comments

total number of combinations-make 2 people as 1 group

(7-1)! - ((6-1)!/2 )

can anyone tell me what is wrong here?

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How are you getting the second term as ((6-1)!/2 )?

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2 girls are never together. I took two girls together ((6-1)!/2 ) and will minus from total number of combinations.