Probability Lesson 3Geometric Probability and the Addition
Rule
The Standard
MCC9-12.S.CP.7 Apply the Addition Rule P{A or B)=P(A)+P(B)-P(A and B), and interpret the answer in terms of the model
Learning Target
I can use geometry or the addition rule to determine probabilities.
Vocabulary
Geometric probability- the probability of an event is based on a ratio of geometric measures such as length or area.
Models for geometric probability
There are three models for geometric probability:
LengthAngle measureArea
Geometric Probability: Length
..
XZ
XY
5
14
XYP
XZ
A point is chosen at random on
Find the probability that the point is on
length
Geometric Probability : Length
1.Look at the example for length. The probability that a point chosen
at random on XZ is on YZ can be
written as
YZP .
2. Write the probability described in Exercise 1 as a percent to the nearest whole percent. ______________________
Geometric Probability: Angle Measure
angle measure
Find the probability that the pointer does not land on white.
360 60 300 5
360 360 6P
Geometric Probability: Angle Measure
3. Look at the example for angle measure. What is the probability that the pointer DOES land on white? ______________________
4. How is your answer to Exercise 3 related to the answer in the example? Why?
angle measure
Find the probability that the pointer does not land on white.
360 60 300 5
360 360 6P
Geometric Probability: Area
area
Find the probability that a point chosen randomly inside the rectangle is in the square.
Area of the rectangle:
A bh 25(10) cm2 250 cm2
Area of the square: A s
2 (5)2 cm2 25 cm2
25 1
250 10P
Geometric Probability: Area
5. Look at the example for area. Find the probability that a point chosen randomly inside the rectangle is in the parallelogram. ______________________
area
Find the probability that a point chosen randomly inside the rectangle is in the square.
Area of the rectangle:
A bh 25(10) cm2 250 cm2
Area of the square: A s
2 (5)2 cm2 25 cm2
25 1
250 10P