If you roll a 2 you will get no homework. What are your chances of getting no homework?

First we need to find out what could happen when we roll the dice. Find all of the possible things that could happen . These are called the outcomes.

The specific outcome we are looking for is 2. This is called the event. In this experiment we have 1 chance of getting a 2

The outcomes are1,1:1,2:1,3:1,4:1,5:1,6 If we continue this pattern we will have 36 possible outcomes.

In words, the probability of an event is the ratio of the number of ways an event can occur to the number of possible outcomes.

In symbols P(event) =The number of ways the event can occur

Number of possible outcomes

In our experiment

P(2) = 1

36

So the probability of getting no homework is

one in thirty-six

Course 1 wb 14-1

The cafeteria is offering the above items for lunch. For $ 3 you get one item from each section.

Main Dish DesertDrinks

If the menu stays the same how many different meals could you eat?

One way to find out is by listing all of the possible outcomes which is called the Sample space.

By following down the branches you can determine all of the possible choices or outcomes and see the entire sample space. Course 3 wb 13-1

A tree diagram can be made horizontally and by using words or letters to represent the choices.

HB

P

HD

PIE

IC

M

IT

Main Dish Desert Drinks

HB

HD

P

PIE

PIE

PIE

IC

IC

IC

M

M

M

M

M

M

IT

IT

IT

IT

IT

IT

Outcomes HB,PIE,M

HB,PIE,IT

P,PIE,M

P,IC,M

P,IC,IT

HD,PIE,M

HD,PIE,IT

HD,IC,M

HD,IC,IT

HB,IC,M

HB,IC,IT

P,PIE,IT

Course 2 wb13-1

When looking for just the total number of outcomes, using the Fundamental Counting Principle is quick and easy.

The lunch problem had 3 groups of choices. Multiplying the number of choices in each group provides us with the number of outcomes. There are 12 different lunch combinations.

Main dishes Deserts Drinks

3 x 2 x 2 = 12

Course 2 wb13-2 course 3 13-1

Theoretical probability is a mathematical computation using the ratio

The number of ways the event can occur

Number of possible outcomes

This type of probability can allow us to predict what could happen. But what actually happens may be different.

If a coin is flipped we can get heads or tails. Our theoretical probability of heads is 1/2.To find out how many heads we could expect in ten trials (flips) multiply 1/2 by 10 (5 heads).

1234

Roll the die Spin the spinner Flip the coin

To find P(1,3,H) use the fundamental counting principle

P(1) P(3) P(H)

1/6 x 1/4 x 1/2

P(1,3,H) = 1/48

This is the theoretical probability. Course 3 13-5 course 2 13-6

The previous experiment is an example of an independent event. (The roll of the die had no impact on the the spinner or the coin)

Experiment: Pick a ball from box 1 and place it in box 2. Then pick a ball from box 2. What is P(B)?

In box 1 a black or white ball can be picked.What happens in box 2 is dependent on what happens in box 1 since the # of each color will change depending on what is picked from box 1. This experiment is a Dependent Event.

A tree diagram can be very helpful in working with Dependent Events.

W

B

2/3

1/3

W2/4

B2/4

W

B

1/4

3/4

OUTCOMESWW

WB

BW

BB

First, draw the diagram and list the P on each branch. Next label the possible outcomes.

Then multiply along the branches to get the P of each outcome.

P

2/3 x 2/4 = 4/12

2/3 x 2/4 = 4 /12

1/3 x 1/4 = 1/12

1/3 x 3/4 = 3/12

Finally, add the events that end in B:4/12 +3/12 =7/12

Theoretical probability is based on mathematical principles.

Experimental Probability is an estimated probability based on the relative frequency of positive outcomes occurring during an experiment.

Experimental probability does not always coincide with theoretical probability. Many organizations use experimental probability to make predictions or forecasts of future trends. Surveys are often used to obtain the data for the basis of the experimental probability.

Course 2 wb13-3

KROC 92.3 WPLJ 95.5 Z 100 KTU 103.5 Q 104.36TH GRADERS 24 30 13 43 217TH GRADERS 26 32 15 38 19

Below are the results of a survey of the 6th and 7th grade students in Norwood. If there are 325 - 6th graders and 350 - 7th graders in the Valley, about how many of each class will prefer KROC?

The survey represents a sample population. We can use this data to obtain an experimental probability. However, it is only useful when applied to a similar population. (For example using this data to predict what station their parents might prefer would not be useful because the population “parents” is not similar to the population “6th and 7th graders”)

KROC 92.3 WPLJ 95.5 Z 100 KTU 103.5 Q 104.36TH GRADERS 24 30 13 43 217TH GRADERS 26 32 15 38 19

First, get a total of each population 6th = 131 7th = 130( these will be our denominators)

Next, find the event we are trying to find (KROC92.3

6th = 24 7th = 26). These will serve as our numerators.

24 26

131 130

Then multiply the ratios by the total number of the new population.

24 x 325 = 60 26 x 350 = 70

131 130Course 3 wb 13-7 course 2wb13-5

A sky diver is going to land in the school field. If it is equally likely to land on any part of the field what is the probability he will land in a circle in the middle of the field?

400 feet

125 feet 42 feet

P(circle) = Area of circle

Area of rectangle

A = Pi r * r

=3.14 *21 * 21

=1385 sq ft.

A = l * w

= 400 *125

= 50,000 sq ft

P(circle) = 1385

50,000

= 2.8%

Course 1 wb14-4

Belgium

Italy

The flags of Germany and Italy are made of black, yellow, red, green and white stripes stripes.

How many different flags can be made of these colors using only vertical stripes?

For the 1st color we have 5 choices. After the 1st stripe is used we have 4 choices for the next stripe. Then we have 3 colors left for the 3rd stripe.

To solve we can use the counting principle 5 x 4 x 3 = 60 different flags.

This problem is an example of a permutation. A permutation is an arrangement of objects in which order is important.

Notice that black,yellow and red is not the same flag as red, yellow and black.

In our problem we have 5 choices to be taken or used 3 at a time.

The permutation formula is P(n,r) n is the number of items or choices and r is how many are used or taken at a time

If we were making a flag with 4 stripes our formula would be:

P(5,4) 5 colors(choices) taken 4 at a time (4 stripes)

5 x 4 x 3 x 2 = 120 different flags.

Course 2 wb 13-7 course 3 wb 13-2

How many 4 digit numbers can be made from 3, 5 ,7 ,9?

This is a permutation of 4 things taken 4 at a time P(4,4)

To solve we multiply 4 x 3 x 2 x 1 Another way of writing this is 4!This is read 4 factorial. In words n! is the product of all of the

counting numbers starting with n and counting backwards to 1.

6!

4!

In this problem we have 6 x 5 x 4 x3 x2 x 1

4 x 3 x 2 x 1

In this problem we can simplify.

Our answer is 6 x 5 = 30

Joe, Sam, Tom and Bob are all guards for the basketball team.

In how many ways can the coach choose 2 starting guards?

In this problem Joe and Tom are the same as Tom and Joe.

So the order is not important.

We ca make a list:JS, JT, JB,ST, SB, TB.

These are all of the different combinations since JS and SJ are the same.

So we have six different combinations.

This problem is an example of a Combination. A combination is an arrangement in which the order is not important.

In our problem whether we list Tom and Joe or Joe and Tom, it is still the same combination of players.

The format for combinations is C(n,r) which in words means the number of combinations of n things taken r at a time.

Mathematically we write it: C(n,r) = P(n,r)

r!

The basketball problem can be solved like this:

C(4,2) = P(4,2)2!

= 4 x 3

2 x 1

= 12

2= 6 combinations.

Course 3 wb 13-3 Course 2 wb 13-8