Prepared by Dr. Agatha Shaw, Valencia College, 9/19/2007
http://faculty.valencia.cc.fl.us/ashaw
QUICK REVIEW: CLAST SKILL IV.D.2
Solve real-world problems involving probabilities
Some Guidelines:
* Complement Rule:
)
(
1
)
(
C
A
P
A
P
=
* General Addition Rule: For any two events, the probability of A or B is
)
(
)
(
)
(
)
(
B
A
P
B
P
A
P
B
A
P
+
=
[
0
)
(
=
B
A
P
when A and B are disjoint events.]
* General Multiplication Rule: For any two events, the probability of A and B is
)
|
(
)
(
)
(
A
B
P
A
P
B
A
P
=
[
)
(
)
|
(
B
P
A
B
P
=
when A and B are independent events.]
* Conditional Probability:
)
(
)
(
)
|
(
A
P
B
A
P
A
B
P
=
The table below shows numbers of hours a week spent working on homework assignments.
Hours per week Percent Placement
0.0 - 1.9 10% Beginning Algebra
2.0 - 3.9 20% Intermediate Algebra
4.0 - 6.9 35% Intermediate Algebra
7.0 - 9.9 30% College Algebra
10.0 – 19.9 5% PreCalculus
1. Find the probability that a randomly chosen student spent between 7.0 to 19.9 hours a week.
a) 0.03 b) 0.3 c) 0.7 d) 0.35
2. Find the probability that a randomly chosen student spent less than 7.0 hours a week.
a) 0.65 b) 0.35 c) 0.95 d) 0.35
3. Find the probability that the student chosen is placed into Intermediate Algebra, given that he or she
spent at least 4.0 hours a week on working on homework assignments.
a) 0.35 b) 0.70 c) 0.5 d) 0.55
4. The circle graph below represents the percentages of courses taken by a group of students.
Statistic s
15%
English
25%
Biology
10%
Physic s
15%
Other
35%
If two students are randomly selected from this group of students, find the probability that both
of them took Biology last Summer.
a) 0.10 b) 0.20 c) 0.50 d) 0.01
