For more information, please see full course syllabus of Basic Math

For more information, please see full course syllabus of Basic Math

## Discussion

## Study Guides

## Practice Questions

## Download Lecture Slides

## Table of Contents

## Transcription

## Related Books

### Probability

#### Related Links

- Probability: the measure of an outcome to the total possible outcomes
- Probabilities are often in the form of a fraction
- The top of the fraction is the number of the desired outcome
- the bottom of the fraction is the total number of possible outcomes

### Probability

- Total marbles = 3 + 6 + 3 = 12
- [red/total]
- [(3 ÷3)/(12 ÷3)] = [1/4]

- Total = 4 + 10 + 6 = 20
- [blue/total] = [10/20]
- [(10 ÷10)/(20 ÷10)] = [1/2]

- Total students = 12 + 8 = 20
- [girls/total] = [8/20]
- [(8 ÷4)/(20 ÷4)]

- Total students = 30 + 17 = 47
- [girls/total] = [17/47]

- Total = 7 + 11 + 3 = 21
- [green/total] = [3/21]
- [(3 ÷3)/(21 ÷3)]

- Total = 9 + 15 + 3 + 12 = 39
- [green/total] = [3/39]
- [(3 ÷3)/(39 ÷3)]

- Total = 13 + 12 + 11 + 14 = 50
- [yellow/total] = [14/50]
- [(14 ÷2)/(50 ÷2)]

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

### Probability

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

- Intro 0:00
- Probability 0:05
- Introduction to Probability
- Example: Probability
- Extra Example 1: What is the Probability of Landing on Orange? 3:26
- Extra Example 2: What is the Probability of Rolling a 5? 5:02
- Extra Example 3: What is the Probability that the Marble will be Red? 7:40
- Extra Example 4: What is the Probability that the Student will be a Girl? 9:43

### Basic Math Online Course

### Transcription: Probability

*Welcome back to Educator.com; for the next lesson, we are going to go over probability.*0000

*Probability is the measure of an outcome compared to the total possible number of outcomes.*0007

*It is in the form of a fraction.*0015

*That means we are going to have a top number and we are going to have a bottom number.*0018

*We are going to have a numerator and denominator.*0021

*On the top, you are going to write the number of the desired outcome.*0026

*Basically what are you looking for?--what is it asking for?*0038

*That number is going to go on the top.*0041

*Then on the bottom, you are going to write the total number of possible outcomes.*0045

*Probability is the measure between the part, the part that you want*0060

*or the part that it is asking for over the whole thing or the total.*0066

*That is the ratio; the ratio is between the part to the whole.*0073

*For example, if I have a bag full of marbles, let's say I have one black marble in this bag.*0085

*I have 3 blue marbles; and I have 2 red marbles.*0096

*I want to know what is the probability, what are the chances of picking a blue marble?*0114

*If I close my eyes and reach into the bag and pick one marble,*0122

*what is the probability, what are the chances of picking a blue marble?*0126

*That would be the number of blue marbles is going to go on the top.*0133

*Blue marbles over... remember the bottom is always the total number, the total number of marbles.*0138

*This is going to be my probability.*0150

*How many blue marbles do I have?*0153

*I have 3; that is my desired outcome.*0155

*I am asking you what are the chances of me picking a blue?*0157

*There are 3 blue marbles; it is going to be 3 on the top.*0162

*Over... how many marbles do I have in all?*0167

*1, 2, 3, 4, 5, 6; 6; my probability is 3/6.*0170

*Since this is a fraction, I need to simplify it.*0179

*If 3/6, then I have to divide this by 3, divide this by 3.*0183

*This becomes 1; 6 divided by 3 is 2.*0190

*The probability of picking a blue marble from this bag of marbles is 1 to 2 or 1/2.*0194

*Let's go over some examples.*0204

*The first example, what is the probability of landing on orange?*0208

*Here I have a pie chart that is divided up into 1, 2, 3, 4, 5 different colors.*0214

*Orange, purple, yellow, green, red; what is the probability...*0223

*If I spin this spinner, what is the probability of landing on orange?*0227

*That means orange is my desired outcome; that is what I am asking for.*0234

*The orange is going to go on the top.*0239

*The total or the whole thing is going to go on the bottom.*0245

*How many orange sections do I have?--I only have 1.*0251

*Then I am going to put 1 on the top.*0256

*How many different sections do I have?--1, 2, 3, 4, 5.*0260

*Out of 5 sections, 1 of them is orange.*0266

*That is why the top number is 1.*0269

*On the bottom, I am going to put 5 because that is the total.*0272

*The probability of landing on orange is going to be 1/5.*0275

*Again it is part to whole; so 1 to 5 is the probability.*0281

*If I ask you what is the probability of landing on purple?*0289

*There is 1 purple out of total of 5 different colors.*0292

*It will be the same thing, 1/5.*0297

*The next example, each side of a dice has a number from 1 to 6.*0304

*What is the probability of rolling a 5?*0310

*We know what a dice is; it is a cube that looks like this.*0313

*Each side has a number representing dots usually.*0322

*One side will have 1; the other side will have maybe 2.*0330

*One side will have 3; another side might have 4 like that.*0334

*There are 6 sides; each side has a different number of dots.*0341

*I want to know what the probability of rolling a 5 is.*0350

*The desired outcome, the top number is going to be rolling a 5.*0354

*Then the bottom number is going to just be the total or the total number of numbers.*0363

*Even though this is a number, that is not the actual number I am going to write on the top for my probability*0371

*because there is not 5 of something; there is not five 5s.*0378

*How many 5s do I have on this?--how many sides have 5 dots?*0382

*Only 1 because each side has a different number.*0389

*There is only one side that will have 5 dots.*0393

*That means I have to put 1 here because it is the number of this desired outcome.*0397

*It is not what this number is.*0403

*It is not that this is a 5 and I have to write the 5 up here.*0406

*It is how many sides do I have with 5 dots?--that is just 1.*0409

*How many total number of sides do I have?--6.*0417

*because again when you are rolling a dice, you are looking to see what the top side is going to be.*0422

*How many dots is the top side going to have?*0429

*That is 1 out of 6.*0433

*Same thing if I asked you what is the probability of rolling a 2?*0437

*Isn't this roll a 2 right now?*0441

*How many sides have a 2?--only one side does.*0445

*It will be the same thing, 1 out of a 6 possible sides.*0449

*1/6 is the probability.*0455

*More marbles; there are 2 red marbles, 5 blue marbles, and 3 green marbles in the bag.*0464

*Let me draw my bag; I have 2 red; red, red.*0475

*I have 5 blue; 1, 2, 3, 4, 5; blue, blue, blue, blue, blue.*0484

*I have 3 green; 1, 2, 3; green, green, green.*0494

*What is the probability that the marble will be red?*0503

*That is my desired outcome; that is the part that is asked for.*0506

*That is going to go on the top; red over total; that is my probability.*0513

*How many reds do I have?--I have... it says here 2 red; red and red.*0522

*2 out of... how many do I have in all?--1, 2, 3, 4, 5, 6, 7, 8, 9, 10.*0534

*1, 2, 3, 4, 5, 6, 7, 8, 9, 10 total marbles.*0544

*My probability would be 2 out of 10.*0550

*Again this is still a fraction; I have to simplify it.*0554

*I know that because the top number and the bottom number are both even numbers,*0560

*I can divide both of them by a 2.*0563

*2/10 becomes... 2 divided by 2 is 1; over... 10 divided by 2 is 5.*0568

*The probability of picking a red is 1 out of 5.*0577

*The fourth example, there are 6 boys and 5 girls in a room.*0585

*If one student is chosen at random, what is the probability that the student will be a girl?*0592

*Again my desired outcome, girl over total.*0601

*I now that there are 5 girls; number of girls is going to be 5.*0611

*On the bottom, I am not writing the number of boys.*0620

*Be careful with this type of example because when it comes to ratio which we learned a few lessons ago,*0623

*if I ask for the ratio of girls to boys, then I would put 5 on the top and 6 on the bottom*0630

*because that would represent girls to boys.*0637

*But this is probability; this is girls to total number of students.*0640

*The bottom number for probability is always the total.*0647

*How many students do I have in all?--5 out of how many in all?*0652

*I would have to add the number of boys and the number of girls*0658

*to figure out how many total number of students there are.*0662

*If I have 6 boys and 5 girls, then I have 11 students in all.*0666

*The total I am going to write is 11.*0674

*Girls, 5; there is 5 girls; out of 11 students.*0677

*The probability is 5/11; this is the probability.*0685

*If they ask for the ratio of girls to boys, then it would be 5 to 6.*0692

*But again probability is different; total number has to go on the bottom.*0702

*That is it for this lesson; thank you for watching Educator.com.*0707

0 answers

Post by Ramez Hajelsawi on March 27, 2013

i know this