Question

find the number of ways in which 5 people A,B,C,D,E can be seated at round table?

Answer 1

Step-by-step explanation:

12 Ways A and B must always sit together   or C and D must not sit together​

Step-by-step explanation:

a)A and B must always sit together

taking ( A & B) as 1  

so total = 4

4 can be seated on round table in (4 - 1) = 3! = 6 ways

A & B can be seated  in 2 Ways

Total ways = 6 * 2 = 12

12 Ways A,B,C,D and E can be seated at a round table such that  A and B must always sit together

b) C and D must not sit together​

Total ways 5 people can sit on circular table = 4! = 24 Ways

12 Ways if C&D are together

C and D must not sit together​ = 24 - 12 = 12 Ways

12 Ways A,B,C,D and E can be seated at a round table such that C and D must not sit together​