00:01
For problem 39, we have to work with seating arrangements in which there are eight seats, and there are four women and four men.
00:12
And in situation a, the women have to be seated together and the men have to be seated together.
00:18
So it can either be all men and all women or vice versa.
00:24
So how do we work this out? well, in the first seat, there's eight possibilities as either as any man or woman could be sat there.
00:33
However, in the second seat, there's only three possibilities, as this will determine which gender now has to sit next to them.
00:40
So if it's a male who is selected, there must only be a man left, and there's only three men left, since one of the four has already been picked.
00:49
Then next to them must also be a man, which there's only two options left, and for the four seat, there's only one option left for men.
00:57
So now, however, it goes back, and there must be a female sitting here.
01:03
And since there's still four females remaining, there's four options for this seat.
01:07
The seat next to her, there's three options.
01:10
Seat next to her, there's two options, and finally there's only one female left.
01:15
So we now multiply all of these together, eight times three times two times one, times four times three times two times one...