00:01
In this problem we're interested in strings of five hexadecimal digits or hexits.
00:13
So to find all possibilities, so we've got five different digits, five different hexits, and some of them could be repeated or not.
00:24
So each of the five has 16 choices.
00:29
So the total is 16 to the fifth, because each one is independently chosen.
00:37
So it's just 16 times itself five times, which comes out to be 104 ,8576.
00:48
In part b, we want to know how many of those have at least one repeat.
01:03
Well to me it seems like there's an easy way and a hard way to do this.
01:06
So let's do it what i think is the easy way, because then we don't have to like track the one, one repeat, two repeats, three repeats, do a lot of calculation.
01:19
Let's just think about five hexadecimal digits.
01:24
So we're supposed to find one with at least one repeat...