9 6 Geometric Probability Warm Up Find the

9 -6 Geometric Probability Warm Up Find the area of each figure. 1. 2. Holt Geometry A = 36 ft 2 A = 20 m 2 3. 3 points in the figure are chosen randomly. What is the probability that they are collinear? 0. 2

9 -6 Geometric Probability Objectives Calculate geometric probabilities. Use geometric probability to predict results in real-world situations. Holt Geometry

9 -6 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, theoretical probability of an event is Holt Geometry

9 -6 Geometric Probability 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. Holt Geometry

9 -6 Geometric Probability Holt Geometry

9 -6 Geometric Probability Example 1 A: Using Length to Find Geometric Probability A point is chosen randomly on PS. Find the probability of each event. The point is on RS. Holt Geometry

9 -6 Geometric Probability Example 1 B: Using Length to Find Geometric Probability The point is not on QR. Subtract from 1 to find the probability that the point is not on QR. Holt Geometry

9 -6 Geometric Probability Example 2 A: Transportation Application A pedestrian signal at a crosswalk has the following cycle: “WALK” for 45 seconds and “DON’T WALK” for 70 seconds. What is the probability the signal will show “WALK” when you arrive? To find the probability, draw a segment to represent the number of seconds that each signal is on. The signal is “WALK” for 45 out of every 115 seconds. Holt Geometry

9 -6 Geometric Probability Example 2 B: Transportation Application If you arrive at the signal 40 times, predict about how many times you will have to stop and wait more than 40 seconds. In the model, the event of stopping and waiting more than 40 seconds is represented by a segment that starts at B and ends 40 units from C. The probability of stopping and waiting more than 40 seconds is If you arrive at the light 40 times, you will probably stop and wait more than 40 seconds about (40) ≈ 10 times. Holt Geometry

9 -6 Geometric Probability Example 3 A: Using Angle Measures to Find Geometric Probability Use the spinner to find the probability of each event. the pointer landing on yellow The angle measure in the yellow region is 140°. Holt Geometry

9 -6 Geometric Probability Example 3 B: 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°. Holt Geometry

9 -6 Geometric Probability 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. Holt Geometry

9 -6 Geometric Probability Example 4 A: Using Area to find Geometric Probability the circle The area of the circle is A = r 2 = (9)2 = 81 ≈ 254. 5 ft 2. The area of the rectangle is A = bh = 50(28) = 1400 ft 2. The probability is P = 254. 5 ≈ 0. 18. 1400 Holt Geometry

9 -6 Geometric Probability Example 4 B: Using Area to find Geometric Probability the trapezoid The area of the trapezoid is The area of the rectangle is A = bh = 50(28) = 1400 ft 2. The probability is Holt Geometry

9 -6 Geometric Probability Example 4 C: Using Area to find Geometric Probability one of the two squares The area of the two squares is A = 2 s 2 = 2(10)2 = 200 ft 2. The area of the rectangle is A = bh = 50(28) = 1400 ft 2. The probability is Holt Geometry

9 -6 Geometric Probability Check It Out! Example 4 Find the probability that a point chosen randomly inside the rectangle is not inside the triangle, circle, or trapezoid. Round to the nearest hundredth. Area of rectangle: 900 m 2 The probability of landing inside the triangle (and circle) and trapezoid is 0. 29. Probability of not landing in these areas is 1 – 0. 29 = 0. 71. Holt Geometry

9 -6 Geometric Probability Lesson Quiz: Part I A point is chosen randomly on EH. Find the probability of each event. 1. The point is on EG. 3 5 2. The point is not on EF. Holt Geometry 13 15

9 -6 Geometric Probability Lesson Quiz: Part II 3. An antivirus program has the following cycle: scan: 15 min, display results: 5 min, sleep: 40 min. Find the probability that the program will be scanning when you arrive at the computer. 0. 25 4. Use the spinner to find the probability of the pointer landing on a shaded area. 0. 5 Holt Geometry

9 -6 Geometric Probability Lesson Quiz: Part III 5. Find the probability that a point chosen randomly inside the rectangle is in the triangle. 0. 25 Holt Geometry