The average number of students who participated from School A taking all the games together is what percentage of the average number of students who participated from School F taking all the games together ?
Total number of ways without restriction " 61 Total number of ways after taking two girls as one single entity = 51 Two girls can sit in 21 ways among themselves.
.'. Total number of ways that two girls don't sit together = 61 - 51 * 21 - 480