Questions?
REVIEW HW
1
Lesson 10.5
USING
PROBABILITY
FORMULAS AND
WORKING
BACKWARDS
Working with Formulas
Substitute in the
information you have in to
the appropriate formula.
Solve for the missing
piece.
Use your algebra skills.
P(A  B) = P(A) + P(B)
Independent
P(A  B) = P(A)  P(B)
Overlapping
P(A  B) = P(A) + P(B) – P(A  B)
Dependent
P(A  B) = P(A)  P(B|A)
PROBABILITY FORMULAS
Mutually Exclusive
Example 1 – Dependent
P(A  B) = P(A)  P(B|A)
The probability of Sam getting an A on
the Chemistry test is 0.76. The probability
of him getting an A on his Calculus test
and an A on his Chemistry test is 0.494.
What is the probability of him getting an
A on his Calculus test given that he got
an A on his Chemistry test?
0.494 = 0.76  P(B|A)
0.65 = P(B|A)
Example 2 – Independent
P(A  B) = P(A)  P(B)
An optional camp to improve players’
basketball skills was held in the county.
The probability of a kid attending was
0.62. The probability that they attended
and made the honor roll was 0.44. What
is the probability that they made the
honor roll?
0.44 = 0.62  P(B)
0.71 = P(B)
Example 3 – Overlapping (Inclusive)
P(A  B) = P(A) + P(B) – P(A  B)
P(A) = ¼
P(B) = 5/8
P(A  B) = ¾
Find P(A  B)
3 1 5
   P  A  B
4 4 8
1/8 = P(A  B)
Using Probability
Formulas and Working
Backwards
6 Problems
Worksheet