Simple Probability

Simple Probability

Possible Outcomes/Total Outcomes in simplest form

Ex. There are 4 red, 3 purple, and 2 pink jellybeans.

What's P(pink or red)?

Possible out of total= 6/9

Reduce to 2/3

Fill in the Blanks

There are 8 red, 2 blue, and 6 green marbles. What's P(blue or green)?

Fill in the Blanks

What's the probability of getting an even number on a die?

Fill in the Blanks

What is 4/5 as a %?

Finding theoretical probability

• Find the possible outcomes out of the total outcomes

• You may have to set up a proportion.

• Ex: 1/3 of the marbles are blue. How many blue marbles would you expect to pick out of 27 marbles?

• 1/3=x/27

• 1x27 divided by 3

Multiple Choice

3 out of 5 m and m's are red. How many would you expect to have in a bag of 50?

• 30

• 20

• 3

• 10

Multiple Choice

The probability that a student guesses the correct answer to a five​-choice multiple choice question is ​P(correct)=0.2. How many correct answers should a student expect to guess on a test with 40 five​-choice multiple choice​ questions? (hint: find 20% of 40)

• 8

• 10

• 20

• 32

200 Cards were drawn. What's the relative frequency of getting 3 or 4?

Possible/ Total=40/200 which is 1/5.

Fill in the Blanks

What's the relative frequency of getting a number less than 3?( out of 200 cards)

% example

Based on the records for the past several​ seasons, a sports fan believes the probability the red team wins is 0.20. The fan also believes the probability the blue team wins is 0.22. In a season with 120 ​games, how many more games should the fan expect the blue team to​ win?

So figure out 20% of 120 .2x120=24

Then 22% of 120 .22x120=26.4

The blue team will be expected to win about 2 more games.

Fill in the Blanks

Based on the records for the past several​ seasons, a sports fan believes the probability the red team wins is 0.4. The fan also believes the probability the blue team wins is 0.3. In a season with 100 ​games, how many more games should the fan expect the red team to​ win?