00:01
This problem says that roberto brought a bag of cookies that contain five chocolate chip cookies, four peanut butter cookies, nine sugar cookies, and four oatmeal cookies.
00:09
What's the probability that roberto reaches in the bag and randomly selects a peanut butter cookie from the bag, eats it, and then reaches back in the bag and randomly selects a sugar cookie? so we want the probability of two separate things happening, and we're going to multiply these two probabilities together to figure out the probability that both would occur.
00:27
And first we need to figure out the total number of cookies that are in this bag, so we would add up all the possibilities.
00:34
So five plus four, plus nine plus four gives us 22.
00:36
So there's 22 total.
00:38
And like we said before, there's the probability of two events that we need to worry about.
00:43
The probability of the first cookie that he reaches in and grabs and eats is a peanut butter cookie.
00:48
So if we want the probability that on the first grab, we get a peanut butter cookie, there's four peanut butter cookies out of the total 22.
00:55
So four out of 22 is the probability of the first event occurring.
00:59
We're going to multiply by the probability of the second event occurring.
01:04
And the second event after he ate that peanut butter cookie and then reaches into the bag again and randomly selects a sugar cookie would give us nine successes for sugar cookies...