COURSE 2 LESSON 12-5
Compound Events
A box contains the same number of green marbles, orange marbles, and blue marbles. You draw one marble, replace it, and draw a second marble. What is the probability that both marbles you draw are blue?
1
Since of the marbles are blue, the probability of drawing a blue marble is .
3
1
3
P (blue, then blue) = P (blue)

P (blue)
Selecting blue is the first and second event.
1
=
 1
3
Substitute.
=
1
9
Multiply.
1
The probability that both marbles will be blue is .
9
12-5

COURSE 2 LESSON 12-5
Compound Events
A spinner has equal sections labeled 1 –10. Suppose you spin twice. Find P (2 and 5).
The two events are independent. There are 10 possibilities on each spin.
P (2 and 5) = P (2)

P (5)
Selecting 2 is the first event.
Selecting 5 is the second event.
1
=
 1
10
=
1
100
Substitute.
Multiply.
1
The probability that you will spin a 2 and a 5 is .
100
12-5

COURSE 2 LESSON 12-5
Compound Events
You select a card at random from those having A, E, I, O, U,
P, C. The card has the letter E. Without replacing the E card, you select a second card. Find the probability of selecting a card that does not have a vowel.
There are 6 cards remaining after selecting an E card.
P (not vowel) =
2
6 number of cards not a vowel number of cards remaining
P (not vowel) =
1
3
Simplify.
1
The probability of selecting a non-vowel for the second card is .
3
12-5

COURSE 2 LESSON 12-5
Compound Events
A bag contains 3 red marbles, 4 white marbles, and 1 blue marble. You draw one marble. Without replacing it, you draw a second marble. What is the probability that the two marbles you draw are red and white?
The two events are dependent. After the first selection, there are 7 marbles to choose from.
P (red, then white) = P (red)

P (white after red)
Use the formula for dependent events.
3
=
 4
7
Substitute.
12-5

COURSE 2 LESSON 12-5
Compound Events
(continued)
=
12
56
Multiply.
=
3
14
Simplify.
3
The probability that the two marbles are red and white is .
14
12-5

COURSE 2 LESSON 12-5
Compound Events
Find each probability.
1.
You roll a number cube twice. What is P (2 and even)?
1
12
2.
You draw a card at random from a stack of ten cards, each labeled with a number from 1 through 10. Then you draw a second card. What is P (5, then 3)?
1
90
12-5