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## Probabilités simples

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# Finding probablity example 3

## Video transcript

Find the probability of pulling
a yellow marble from a bag with three yellow, two red,
two green, and one blue marbles, I'm assuming. So let's just think about
this bag a little bit. There are three yellow
marbles in it. So let me draw them. We have one, two, three
yellow marbles. We have two red marbles. So we have one, two red marbles,
assuming they're all mixed in there. We have two green marbles--
one, two green marbles. And then there's one
blue marble. And they want to know the
probability of pulling a yellow marble. So they want to know what is the
probability of pulling a yellow marble. Now probability is just a way of
expressing-- well, I don't want to use too loaded words. But it's the odds of picking
yours relative to the odds of picking everything else. Or another way of thinking about
it is, it's the number of outcomes that could result
in what you want, a yellow marble, over the total
number of outcomes. So how many ways are there-- how
many events-- you're going to pick out a ball. How many of those-- how many
ways-- or how many balls can you pick out that
will be yellow? Well, there's three balls. There's three balls that you
can pick out as yellow. One, two, and three. We're assuming that they're
all equally likely to be picked up. They're all mixed in there. So there's three yellow balls
you could pick up. Now how many total
balls are there? How many total balls are
there to be picked up? Well, you could be picking up
any one of eight balls, right? One, two, three, four, five,
six, seven, eight. So there's a total number
of eight balls. So the probability of picking
a yellow marble is 3/8. So you have a 3/8 chance of
picking a yellow marble. And just a way to
think about it. I just want to reiterate. It's just the number
of outcomes. There's eight total outcomes. There's eight different
things that you could pull out of the bag. Three of them satisfy
your conditions. Three of them would be
a yellow marble.