12-7 Probability of Compound Events

(AND problems)Goal: Find the probability of a compound event.

Eligible Content:A1.2.3.3.1

Independent Events – the outcome of one event does not affect the outcome of another event. Probability of picking a red marble and

a green marble from a bag. Dependent Events – the outcome of

one event affects the outcome of another event. Probability of picking a student who is a

girl and wears glasses.

Vocabulary

Multiply the probabilities together.

P(A and B) = P(A) * P(B)

Leave answers as fractions!!!

Independent Events

Multiply the probabilities together, but be careful when finding second probability.

P(A and B) = P(A) * P(B)

Leave answers as fractions!!!

Dependent Events

A bag of marbles contains 4 black, 8 blue, 6 yellow and 5 green marbles. A marble is selected, replaced, and a second marble is selected. Find the probability of selecting a black marble, then a yellow marble.

Independent

P(black, yellow) =

Example #1

At a carnival, winners in the ring-toss game are randomly given a prize from a bag that contains 4 sunglasses, 6 hairbrushes, and 5 key chains. Two prizes are randomly drawn from the bag and not replaced. Find the probability of selecting a hairbrush then sunglasses.

Dependent

P(hairbrush, sunglasses) =

Example #2

A toy bin contains 6 stuffed animals, 4 dolls, 8 puzzles and 2 books. What is the probability of randomly selecting a stuffed animal, replacing it in bin, then selecting a doll?

Independent

P(stuffed animal, doll) =

Example #3

A toy bin contains 6 stuffed animals, 4 dolls, 8 puzzles and 2 books. What is the probability of randomly selecting a puzzle, then selecting a book without replacing the first toy?

Dependent

P(puzzle, book) =

Example #4

There are 12 books on a table. There are 5 math books, 2 biology books, 4 social studies books, and 1 Spanish book. What is the probability of randomly selecting a math book, returning it to the table, then selecting a biology book?

Independent

P(math, biology) =

Example #5

There is a candy dish on the table. In the dish there are 5 Snickers bars, 2 Kit Kats, 4 Reese’s peanut butter cups, and 7 Milky Way bars. What is the probability of randomly selecting a Snickers bar, eating it, then selecting a Milky Way bar?

Dependent

P(Snickers, Milky Way) =

Example #6

Page 797 #1-4

Practice

Pages 797-798 #11,13,14 #19-23

Homework