Back To Course

GED Math: Quantitative, Arithmetic & Algebraic Problem Solving9 chapters | 66 lessons

Watch short & fun videos
**
Start Your Free Trial Today
**

Instructor:
*Betsy Chesnutt*

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Understanding percents can help you quickly determine how much things cost and many other things. In this lesson, you will learn what percents are and how to use the percent formula.

I went to the store yesterday and saw a shirt I really liked. The tag said it cost $37.99, but it was currently on sale for 30% off. I only had $30 with me. Was that enough to purchase the shirt or not? What exactly does a percent represent and how can we use it to calculate the cost of my new shirt?

The word **percent** comes from the Latin words *per centum* which means *by the hundred*, so a percent tells you how many parts you have out of 100 total. For example, if you had a bag full of 100 different colored marbles and I told you that 25% of the marbles in the bag were red, then you would know that exactly 25 of the marbles were red. Similarly, if my shirt cost exactly $100, I would know that 30% of $100 was $30, so the shirt would cost $70 ($100-$30 = $70).

Percents can also be written as fractions or decimals. To convert a percent to a fraction, simply divide it by 100. That means that 30% could be written as 30/100 or 3/10. This could also be written as a decimal (3/10 = 0.3).

Percents are really easy to calculate when you have exactly 100 things, but it's rare for the amount of something to be exactly 100. Percents are still really useful though, and we can use the percent formula to calculate percents of any amount!

To find a percent of any number, you can use the percent formula where:

**Part** = the part of the whole

**Whole** = the total amount that the percent is operating on - also known as the base

**Percent (%)** = the number of parts per 100 - also known as the rate

Let's look at three different examples of how you could use the percent formula.

First, we will look at how to find the part that is a percentage of a whole amount. This is exactly what I needed to do when I wanted to know if I could buy the new shirt. I knew the total amount (the total cost of the shirt - $37.99) and the percent (30%), and needed to find 30% of the whole so I would know how much the shirt would actually cost. To do this, we can cross multiply and solve for the part:

We could round this to $11.40 since you can't pay part of a cent. So, how much will the shirt cost then? If the original price was $37.99 and it is 30% off, we can subtract the part we just found from $37.99 to find the new price:

$37.99 - $11.40 = $26.59

So, I would have enough money to buy the shirt!

To find the whole when you know the part and base, you will have to cross multiply again and then solve for the base. As an example, let's say that you know that 40% of a box full of apples are green and the rest are red. You know that there are exactly 20 green apples, so how many apples are there total in the box?

In this case, 40% is the percent and 20 is the part. Now what is the whole (the total number of apples)?

There are a total of 50 apples in the box. 20 are green, which means that 30 must be red.

Once again, to find the percent if you already know the whole and part, you can use the percent formula, but you must cross multiply and then solve for the percent. Let's try an example. Suppose that in a classroom there are 30 students and 12 of the students are girls. What percent of the students in the class are girls?

30 would be the whole and 12 would be the part, so let's see how to find the percent:

In this class, we have determined that 40% of the total students are girls.

A **percent** tells you how many parts you have out of one hundred. You can use the percent formula to calculate any quantity if you know the other two.

To unlock this lesson you must be a Study.com Member.

Create your account

Already a member? Log In

BackDid you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

You are viewing lesson
Lesson
2 in chapter 5 of the course:

Back To Course

GED Math: Quantitative, Arithmetic & Algebraic Problem Solving9 chapters | 66 lessons

- Communications 105: Intro to Mass Communications II
- Chemistry 303: Organic Chemistry I
- View High School: Biology
- Introduction to Purpose-Driven Sales
- Computer Science 311: Artificial Intelligence
- Noble Sales Techniques
- Working with Management in Sales
- Building Your Sales Network
- Cultural Impact of Television
- Sales Calls & Presentations
- FTCE Prep Product Comparison
- TExES Prep Product Comparison
- Study.com ASVAB Scholarship: Application Form & Information
- Study.com GED Scholarship: Application Form & Information
- Study.com GACE Scholarship: Application Form & Information
- Study.com CSET/CBEST Scholarship: Application Form & Information
- Study.com NES Scholarship: Application Form & Information

- Using Cross-Tabulation Reports in Marketing Research
- The Child-Saving Movement: History, Goals & Outcomes
- Designing Marketing Research Questionnaires
- Statistical Software for Marketing Research
- Unsupervised Learning in Machine Learning
- Practical Application for Data Structures: Stacks, Queues & Linked Lists
- Cultural Differences in Oral & Written Discourse
- Developing a Mission Statement & Philosophy for a Library Media Program
- Quiz & Worksheet - HR Negotiation & Bargaining
- Quiz & Worksheet - Bias in Personality Research
- Quiz & Worksheet - Measurement Unit Education
- Quiz & Worksheet - Context Effects & Consumer Choice
- Quiz & Worksheet - Target Market Analysis
- International Law & Global Issues Flashcards
- Foreign Policy, Defense Policy & Government Flashcards

- High School World History: Help and Review
- CLEP English Literature: Study Guide & Test Prep
- CAHSEE Math Exam: Test Prep & Study Guide
- Praxis Psychology: Practice and Study Guide
- CSET Social Science Subtest 1: Practice and Study Guide
- MTTC: Account Types
- OAE - Integrated Social Studies: Economic Systems & Models
- Quiz & Worksheet - Anatomy of the Heart
- Quiz & Worksheet - Solving Trigonometric Equations for X
- Quiz & Worksheet - How Genes Influence Intellectual Abilities
- Quiz & Worksheet - Applying Evolutionary Theory to Learning
- Quiz & Worksheet - Functions of the Lymphatic System

- Bones of the Shoulder: Anatomy and Functions
- Using the ADDIE Model in Instructional Design
- What Is the Syllabus of an Algebra I Course?
- National Bullying Prevention Month
- Telling Time Games & Activities
- 3rd Grade Math Projects
- Next Generation Science Standards in California
- What is Professional Development for Teachers?
- High School Interview Questions & Tips
- Mechanical Engineering Scholarships for High School Seniors
- 504 Plans in Iowa
- Common Core State Standards in Ohio

Browse by subject