{{ toc.name }}
{{ toc.signature }}
{{ toc.name }} {{ 'ml-btn-view-details' | message }}
{{ stepNode.name }}
{{ 'ml-toc-proceed' | message }}
Lesson
Exercises
Recommended
Tests
An error ocurred, try again later!
Chapter {{ article.chapter.number }}
{{ article.number }}. 

{{ article.displayTitle }}

{{ article.intro.summary }}
{{ 'ml-btn-show-less' | message }} {{ 'ml-btn-show-more' | message }} expand_more
{{ 'ml-heading-abilities-covered' | message }}
{{ ability.description }} {{ ability.displayTitle }}
{{ 'ml-heading-lesson-settings' | message }}
{{ 'ml-lesson-show-solutions' | message }}
{{ 'ml-lesson-show-hints' | message }}
{{ 'ml-lesson-number-slides' | message : article.intro.bblockCount}}
{{ 'ml-lesson-number-exercises' | message : article.intro.exerciseCount}}
{{ 'ml-lesson-time-estimation' | message }}
In this lesson, some basics concepts of probability will be introduced and connected to real-life situations.

Catch-Up and Review

Here are a few recommended readings before getting started with this lesson.

Explore

Possible Outcomes of Target Shooting

Magdalena is in a target shooting competition. For her next test, the target has three zones and she can shoot three arrows.
A target Shooting and a bow and arrow
Assuming that Magdalena always hit the target, list all the possible results that Magdalena can get on the test.

Challenge

Probability of Winning a Prize

On a late-night game show, there are three closed doors. Behind one of the doors is a car, and there are sheep behind the other two. The host invites Tearrik to win the car by choosing only one door.
Applet to pick a door out of three to try winning the car
a What are the chances that Tearrik will choose the winning door? Round the answer to two decimal places.
b What are the chances of choosing a door with a sheep? Round the answer to two decimal places.

Discussion

Defining Experiments in Probability

Below, some basic definitions of probability are examined.

Concept

Event

An event is a combination of one or more specific outcomes. For example, when playing cards, an event might be drawing a spade or a heart. For this event, one possible outcome is drawing the or drawing the

A deck of cards, a 7 of hearts, and the ace of spades

However, these are not the only outcomes of this event. All the possible outcomes that satisfy the event are listed below.

Example

Sample Space: Drawing Marbles From a Bag

Paulina bought two white and three black marbles, all of different sizes, and put them in a bag. When she got home, her little brother Diego and sister Emily asked her to give them two marbles. Paulina agreed but told them to draw one marble each without looking inside the bag. Diego drew the first marble, then Emily.

A bag, 2 white marbles, and 3 black marbles
a Assuming all the marbles are distinguishable, write down the sample space for the event of Diego and Emily randomly drawing two marbles from the bag. What is the total number of outcomes?
b How many of the outcomes in the sample space represent the case where Diego and Emily both drew white marbles?
c How many of the outcomes in the sample space represent the case where Diego and Emily both drew black marbles?
d How many of the outcomes in the sample space represent the case where Diego and Emily drew marbles of different colors?
e In a few words, write a different event for the situation presented.

Answer

a Number of Outcomes:

Outcomes:
Here, and represent the white marbles, and and represent the black marbles.
b Number of Outcomes:

Outcomes: and

c Number of Outcomes:

Outcomes:
d Number of Outcomes:

Outcomes:
e Example Event: Diego and Emily ask Paulina to give them two marbles each.

Hint

a Give each marble a label. How many outcomes does the first drawn marble have? How many outcomes does the second marble have?
b Look for the outcomes containing only the labels assigned to the white marbles.
c Look for the outcomes containing only the labels assigned to the black marbles.
d Look for the outcomes containing one label assigned to the white marbles and one label assigned to the black marbles.
e If Diego and Emily ask for a different number of marbles, this is a different event.

Solution

a Despite having only two colors, all five marbles are said to be distinguishable. That is why starting by labeling each of the marbles is a good option.
A bag, 2 white marbles, and 3 black marbles

Since both marbles are randomly drawn, each outcome of the event will consist of two labels. For the first marble, there are possible outcomes. For the second marble, there are possible outcomes because one marble has already been removed from the bag.

A two-element set where the first element comes from the first marble drawn and the second element comes from the second marble drawn
Since the Diego draws a marble first and Emily draws a marble after him, the order in which the marbles are drawn matters. Therefore, the outcomes and are different. The following table lists all the possible outcomes for the event of drawing two marbles from the bag.
Consequently, there are a total of possible outcomes in the sample space.
b The case in which two white marbles are drawn is represented by the outcomes containing only and From Part A, it can be seen that there are only two such outcomes — and
c The case in which two black marbles are drawn is represented by the outcomes containing neither nor Analyzing the sample space from Part A, six such outcomes can be found.
d The case in which one white and one black marble are drawn is represented by the outcomes containing one label and one label. From Part A, there are twelve such outcomes.
e There are an infinite number events that can be considered. For example, Diego and Emily could ask Paulina to give them two marbles each. In that case, the event would be the drawing of four marbles.

Discussion

Probability of the Complement of an Event

The probability of drawing a club from a standard deck of cards is Knowing this, what is the probability of drawing a spade, heart, or diamond if a card is drawn randomly?

Cards from the As to K

To figure it out, instead of counting the favorable outcomes, the complement rule can be used.

Applying this formula, the probability of drawing a spade, heart, or diamond can be computed.