00:01
We're looking at a lottery.
00:03
You pick three numbers, and you can choose any number from 0 -000 to 999.
00:09
First question is how many possible numbers can you choose? well, it's going to be 1 ,000.
00:15
You get three digits.
00:17
Each digit is 0 to 9, so you have 10 possibilities.
00:21
10 from the 1st times 10 times 10 is 1 ,000 different possibilities.
00:28
Part b, if all three -digit numbers are equally likely, what's your probability of winning? so you pick one of the numbers out of a thousand, which means that your chance of winning the exact number is one in a thousand.
00:46
Let's see.
00:47
You pick 156 and you can win if you have the correct three digits.
00:55
So now we make things a bit more complicated.
01:00
So we have 1 .56 and you will win if the correct answer is 1 .5.
01:05
But you will also win if it's 516, you will also win if it's 615, and so on.
01:20
So now the question is how many different ways are there of putting these three digits in order? and we can work that out by saying, okay, i have three digits.
01:32
For my first digit, i have three options.
01:36
This could be a one or a five or a six.
01:38
For my second digit, i only have two options left.
01:42
Let's say the first one is a one, this can now only be a five or a six...