A spinner has 4 equal sectors colored yellow, blue, green, and red. What is
the probability of landing on purple after spinning the spinner?
Probability:
It is impossible to land on purple since the spinner does not contain this
color.
P(purple)
=
0
=
0
4
Experiment 2:
A teacher chooses a student at random from a class of 30 girls. What is
the probability that the student chosen is a girl?
Probability:
Since all the students in the class are girls, the teacher is certain to
choose a girl.
P(girl)
=
30
=
1
30
In the first experiment, it was not possible to land on purple. This is an example of an
impossible event.
In the second experiment, choosing a girl was certain to occur. This is an example of a
certain event.
The next experiment will involve a standard deck of 52 playing cards,
which consists of 4 suits: hearts, clubs, diamonds and spades.
Each suit has 13 cards as follows: ace, deuce, three, four, five, six, seven, eight, nine,
ten, jack, queen, and king. Picture cards include jacks, queens and kings. There are no joker cards. There are
only 4 of a kind, for example, 4 tens.
Experiment 3:
A single card is chosen at random from a standard deck of 52
playing cards. What is the probability that the card chosen is a joker card?
Probability:
It is impossible to choose a joker card since a standard deck of cards
does not contain any jokers. This is an impossible event.
P(joker)
=
0
=
0
52
Experiment 4:
A single 6-sided die is rolled. What is the probability of rolling a number less than 7?
Probability:
Rolling a number less than 7 is a certain event since a single die has 6 sides, numbered 1 through 6.
P(number < 7)
=
6
=
1
6
Experiment 5:
A total of five cards are chosen at random from a standard deck of 52
playing cards. What is the probability of choosing 5 aces?
Probability:
It is impossible to choose 5 aces since a standard deck of cards has
only 4 of a kind. This is an impossible event.
P(5 aces)
=
0
=
0
52
Experiment 6:
A glass jar contains 15 red marbles. If a single marble is chosen at random from
the jar, what is the probability that it is red?
Probability:
Choosing a red marble is certain to occur since all 15 marbles in the jar are
red. This is a certain event.
P(red)
=
15
=
1
15
Summary:
The probability of an event is the measure of the chance that the event will occur as a result of the experiment.
The probability of an event A, symbolized by P(A), is a number between 0 and 1, inclusive, that measures the likelihood
of an event in the following way:
If P(A) > P(B) then event A is more likely to occur than event B.
If P(A) = P(B) then events A and B are equally likely to occur.
If event A is impossible, then P(A) = 0.
If event A is certain, then P(A) = 1.
Exercises
Directions: Read each question below. Select your answer by clicking on its button. Feedback to your answer
is provided in the RESULTS BOX. If you make a mistake, choose a different button.
1.
A glass jar contains 5 red, 3 blue and 2 green jelly beans. If a jelly bean is chosen at random from the
jar, then which of the following is an impossible event?
2.
A spinner has 7 equal sectors numbered 1 to 7. If you spin the spinner, then which of the following
is a certain event?
3.
What is the probability of choosing 14 hearts from a standard deck of 52 playing cards?
4.
If a number is chosen at random from the following list, then what is the probability that it is
prime?
2, 3, 5, 7, 11, 13, 17, 19
5.
If a single 6-sided die is rolled, then which of the following events is neither certain nor impossible?
Interactive Math Goodies Software
![[IMAGE]](images/student_girl.gif)
![[IMAGE]](images/suits.gif)
![[IMAGE]](images/poker_hand.gif)
![[IMAGE]](images/red_marbles.gif)
