Nine children — A, B, C, D, E, F, G, H and I — are going to sit in nine chairs in a row. The children C & F have to sit next to each other, and the others can sit in any order in any remaining chairs. How many possible configurations are there for the children?  Select:
A) 600  B) 720  C) 80640  D) 84320  E) 84800
for such questions , we can treat both as one then total person=8..   these 8 can be arranged in 8! ways.. but within these 8 , one consists of two people who can be arranged in 2 ways CF or FC.. so ans =8!*2=80640   ans 80640
<result>C</result>
Nine children — A, B, C, D, E, F, G, H and I — are going to sit in nine chairs in a row. The children C & F have to sit next to each other, and the others can sit in any order in any remaining chairs. How many possible configurations are there for the children?