Ok, for some reason my answers for the following 3 questions we were given for hw on permutations are wrong (according to the answers in the back of the text).(adsbygoogle = window.adsbygoogle || []).push({});

I was hoping that somebody could point me in the right direction, these basic ones should be simple for me. Thanks!

In how many ways can 11 players be seated on a bench so that Joey and Jill are not seated next to each other?

arrangements = total arrangements - arrangements where they are together

arrangements = 11! - 10!

arrangements = 36 288 000..........text had 32 659 200

In how many ways can four men and four women be seated around a circular table if each man must be flanked by two women?

i arranged the men first, then the women... i said that the first man has 8 possible seats, the second has 3 (because he can't sit beside another man and there has to be room for 2 women beside him) and the third has 2, and the last man has 1 possible seat. This leaves 4 seats for the first women, 3 for the second, 2 for the third, and 1 left for the last women to sit down.

thus, arrangements = (8 x 3 x 2 x 1) + (4!) = 72text had 144

In how many ways can you form a three-digit number using only the digits of the number 21 150?

well, since it has to be 3 digits, 0 cannot be the first or second.

that leave's 4 digits to be put in the first and second places, and 5 for the last. divide by 2! because of the repeated 1.

thus, arrangements = (4 x 4 x 5) / 2 = 40 waystext has 26

-Jon

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# Homework Help: Permutations are these not correct?

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