1. Algebra 1 Notes: Lesson 2-6, Part 1: Simple Probability and Odds

2. Objectives Find the Probability and Odds of simple events
Describe the difference between probability and odds
Switch between probability and odds

3. Vocabulary
Probability

4. Vocabulary Probability
Usually expressed as a fraction – CAN be a decimal or percent.
ALWAYS between 0 and 1

5. Probability
The probability of an event can be expressed as:
P(a) =

7. Example 1
Find the probability of rolling a number greater than 2 on a die.
P(greater than 2) =

8. Example 1
Find the probability of rolling a number greater than 2 on a die.
P(greater than 2) =
About 67%

9. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
a) P(black) =

10. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
a) P(black) = =

11. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
P(black) = =
P(red or brown) =

12. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
a) P(black) = =
b) P(red or brown) = =

13. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
a) P(black) = =
b) P(red or brown) = =
c) P(not blonde) =

14. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
a) P(black) = =
b) P(red or brown) = =
c) P(not blonde) = =

15. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
d) P(green) =

16. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
d) P(green) = = 0 20

17. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
d) P(green) = = 0
e) P(has hair) = 20

18. Example 2
A class contains 6 students with black hair, 8 with brown hair, 4 with blonde hair, and 2 with red hair. Find each probability.
d) P(green) = = 0
e) P(has hair) = = 1 20 20

19. Equally Likely 0 ½ 1 impossible equally likely certain
0 ½
impossible equally likely certain
to occur to occur to occur

20. Vocabulary
Odds

21. Favorable : Unfavorable
Odds
Favorable : Unfavorable

22. Example 3 Find the odds of rolling a number greater than two on a die.
Numbers greater than two: 3, 4, 5, 6
Numbers not greater than two: 1, 2
Odds = 4:2

23. Example 3 Find the odds of rolling a number greater than two on a die.
Numbers greater than two: 3, 4, 5, 6
Numbers not greater than two: 1, 2
Odds = 4:2 or 2:1

24. Example 4
A card is selected from a standard deck of 52 cards. What are the odds against selecting a 2 or 3?
Not a 2 or 3:

26. Example 4
A card is selected from a standard deck of 52 cards. What are the odds against selecting a 2 or 3?
Not a 2 or 3: 44
2 or 3:

28. Example 4
A card is selected from a standard deck of 52 cards. What are the odds against selecting a 2 or 3?
Not a 2 or 3: 44
2 or 3: 8
Odds = 44:8

29. Example 4
A card is selected from a standard deck of 52 cards. What are the odds against selecting a 2 or 3?
Not a 2 or 3: 44
2 or 3: 8
Odds = 44:8 or 11:2

30. Switch between probability and odds1)

31. Switch between probability and odds
1) :

32. Switch between probability and odds
1) 3 : 1 2) 5 : 3

33. Switch between probability and odds
1) 3 : 1 2) 5 : 3 ⅝

34. Homework
Pgs. 99: Evens