18.1 Geometric Probability

Remember that in probability, the set of all possible outcomes of an experiment is called the sample space. Any set of outcomes is called an event. If every outcome in the sample space is equally likely, the theoretical probability of an event is

Geometric probability is used when an experiment has an infinite number of outcomes. In geometric probability, the probability of an event is based on a ratio of geometric measures such as length or area. The outcomes of an experiment may be points on a segment or in a plane figure.

If an event has a probability p of occurring, the probability of the event not occurring is 1 – p. Remember!

Example 1A: Using Length to Find Geometric Probability A point is chosen randomly on PS. Find the probability of each event. The point is on RS.

Example 1C: Using Length to Find Geometric Probability The point is on PQ or QR. P(PQ or QR) = P(PQ) + P(QR)

Example 3B: Using Angle Measures to Find Geometric Probability Use the spinner to find the probability of each event. the pointer landing on blue or red The angle measure in the blue region is 52°. The angle measure in the red region is 60°.

Example 3C: Using Angle Measures to Find Geometric Probability Use the spinner to find the probability of each event. the pointer not landing on green The angle measure in the green region is 108°. Subtract this angle measure from 360°.

Example 4: Using Area to find Geometric Probability Find the probability that a point chosen randomly inside the rectangle is in each shape. Round to the nearest hundredth. circle trapezoid 1 of 2 squares leftover

Assignment Pg. 597-598 (2-26) Omit 6, 7, 20, 21, 22