Question

Krystal buys a bag of cookies that contains 9 chocolate chip cookies, 7 peanut butter cookies, 7 sugar cookies and 7 oatmeal raisin cookies. What is the probability that Krystal randomly selects a peanut butter cookie from the bag, eats it, then randomly selects another peanut butter cookie? Express your answer as a reduced fraction.

Answer 1

7/145

Explanation:

We have

9 chocolate chip cookies

7 peanut butter cookies

7 sugar cookies

7 oatmeal raisin cookies.

9+7+7+7 = 30 cookies.

What is the probability that Krystal randomly selects a peanut butter cookie from the bag, eats it, then randomly selects another peanut butter cookie?

Initially, there are 30 cookies, 7 of which are peanut butter cookies. So the probability that Krystal selects a peanut butter from the bag is 7/30.

Suppose she selected the peanut butter cookie. Now there are 29 cookies, of which 6 are peanut butter. So the probability that the second one is a peanut butter cookie is 6/29.

Probability that both are peanut butter cookies:

Multiplication

`P = (7)/(30)(6)/(29) = (7)/(145)`