✔ 最佳答案
Step 1 :The athlete who can only on left side have 4 ways to sit.Step 2 :2 athletes who can only on right side have 4C2 ways to sit.Step 3 :Other 5 athletes have 5! ways to sit.Answer is 4 * 4C2 * 5! = 2880 arrangement.
2011-09-12 13:03:05 補充：
The given answer 2880 is wrong!!
The correct answer is 4 * 4P2 * 5! = 5760
2011-09-12 13:05:25 補充：
(Arrange the left-side athlete to 1 of the 4 placeson the left.)
(Then, arrange the 2 right-side athletes to 2 of the 4 places on the right.)
(Finally, arrange the rest 5 athletes to the rest 5 places.)
Number of ways that the coach can arrange the athletes
= 4P1 * 4P2 * 5P5
= 5760
2011-09-12 13:05:50 補充：
Alternative method:
(From the rest 5 athletes, choose 3 to the left.)
(Arrange these 3 athletes and the left-side athlete to the 4 places on the left.)
(Arrange the rest 4 athletes to the 4 places on the right.)
No. of ways
= 5760
2011-09-12 13:06:22 補充：
(= 5C3 * 4P4 * 4P4 )
2011-09-12 13:07:21 補充：
.
2011-09-12 13:08:16 補充：
http://hk.knowledge.yahoo.com/question/question?qid=7011052901437
落選答案
2011-09-12 13:21:21 補充：
Also see :
http://hk.knowledge.yahoo.com/question/question?qid=7011050400533
2880 is WRONG!!!!
2011-09-12 13:22:15 補充：
Donn't trust your book!!
