1. Lesson 1.9 Probability Objective: Solve probability problems

2. Two Basic Steps for Probability Problems: 1.Determine all possibilities in a logical manner. Count them. 2.Determine the number of these possibilities that are “favorable.” (We call these “winners”) For Starters: Probability = number of winners total number of possibilities

3. Example #1: If one of the four points is picked at random, what is the probability that the point lies on the angle? Practice D C B A Solution: List all possibilities, and circle the “winners” A B C D

4. If two of the four points are selected at random, what is the probability that both lie on ? More Practice D C B A Solution: List all possibilities, and circle the “winners” AB BC CD AC BD AD

5. If three of the four points are selected in a random, order, what is the probability that the ordered letters will correctly name the angle shown? Even More Practice! D C B A Solution: List all possibilities, and circle the “winners” ABC BAC CAB DAB ABD BAD CAD DAC ACB BCA CBA DBA ACD BCD CBD DBC ADB BDA CDA DCA ADC BDC CDB DCB

6. Even More Practice! D C B A ABC BAC CAB DAB ABD BAD CAD DAC ACB BCA CBA DBA ACD BCD CBD DBC ADB BDA CDA DCA ADC BDC CDB DCB

7. A point Q is randomly chosen on. What is the probability that it is within 5 units of C? Hang in there….last one! C AB 3 11 15 Hint: Find the length of the “winning” region and compare it to the total length of the segment!

8. Lesson 1.9 Worksheet Homework