00:01
Suppose i have the word add dresses with two ds and two ss.
00:07
Okay, so how many place values do i have? i have one, two, three, four, five, six, seven, eight, nine place values.
00:13
How many permutations of the letters do i have? well, what is a permutation? permutation is just how can i reorganize these letters? so in my first place, how many different letters can go here? we have nine different spaces.
00:27
In my second place, how many letters can go here? i can't, in a permutation, i can't repeat a letter.
00:32
So once i take one away, i have eight left in the third place.
00:36
I take away two.
00:38
I have seven other choices in my fourth place.
00:41
I have now left with one less than seven, six.
00:44
Fifth is five all the way down in my first place, which is one.
00:47
So this is equivalent to just nine factorial, nine times eight, time seven, six, all the way down until one.
00:55
And my total permutations is 360 ,000, 880...