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Pre-Algebra: Foundations for Algebra I

  • Mathematics

Integers, fractions, decimals, expressions, equations, functions, and geometric reasoning form the foundation for Algebra I. This course sharpens arithmetic skills and introduces negative numbers, exponents, proportional relationships, transformations, and data analysis.

Sign in to enroll$1037 lessons

What you'll learn

  • Operations with Fractions and DecimalsFluency with adding, subtracting, multiplying, and dividing fractions and decimals, and converting between the two forms, is essential for solving pre-algebra problems.
  • The Pythagorean TheoremA relationship stating that in a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs.
  • Angle Pair RelationshipsFour special relationships between angles—complementary, supplementary, vertical, and adjacent—let you find one angle's measure from another without measuring.
  • Operations with Positive and Negative IntegersIntegers include positive numbers, negative numbers, and zero, and learning to add, subtract, multiply, and divide them is essential because negative numbers appear in nearly every equation from pre-algebra onward.
  • Slope as Rate of ChangeSlope is the constant rate at which the output of a line changes for each unit change in input, calculated as the ratio of vertical change to horizontal change between two points.
  • Ratios, Rates, and Unit RatesMethods for comparing quantities: ratios compare any two quantities by division, rates compare quantities in different units, and unit rates simplify rates to have a denominator of 1.
  • Solving Multi-Step Linear EquationsA linear equation requiring several operations like distributing, combining like terms, and isolating the variable by repeatedly applying the same operation to both sides.
  • Defining and Representing FunctionsA function is a rule that assigns exactly one output to each input, where the set of all inputs is called the domain and the set of all outputs is called the range.
  • Order of OperationsThe agreed-upon sequence for evaluating math expressions with multiple operations so that everyone gets the same answer.
  • Scatter Plots and Line of Best FitA scatter plot is a graph displaying pairs of numerical values as points to reveal whether two variables tend to change together in a predictable way.
  • Slope-Intercept Form of a LineA linear equation written as y = mx + b where m is the slope and b is the y-intercept, making the steepness and starting point of a line immediately visible.
  • Proportional Relationships and Constant of ProportionalityA relationship between two quantities where one is always a constant multiple of the other, expressed as y = kx where k is the constant of proportionality.
  • Writing Linear Expressions and EquationsThe process of converting real-world descriptions or word problems into mathematical statements using variables, numbers, and operations.
  • Classifying Rational and Irrational NumbersRational numbers can be expressed as a fraction of two integers and have decimals that terminate or repeat, while irrational numbers cannot be written as such a fraction and have decimals that continue forever without repeating.
  • Geometric TransformationsTransformations are moves or resizes of figures on a coordinate plane, including translations, reflections, rotations, and dilations, where the original figure is the pre-image and the resulting figure is the image.
  • Laws of Integer ExponentsRules that simplify expressions with exponents by allowing you to combine like bases without expanding them, such as adding exponents when multiplying powers or subtracting when dividing.
  • Percent ApplicationsReal-world situations where finding a percent of a number is applied, such as calculating discounts, taxes, markups, and interest.
  • Congruence and SimilarityCongruent figures have exactly the same size and shape, while similar figures have the same shape but may differ in size by a consistent scale factor.
  • Two-Way Frequency TablesA table that organizes counts of individuals across two categorical variables simultaneously, showing how many fall into each combination of categories.
  • Scale Drawings and Scale FactorA scale drawing is a proportional representation of a real object that shrinks or enlarges it by a consistent ratio, with the scale factor being the number that relates the drawing's measurements to the actual object's measurements.
  • Surface Area of Three-Dimensional SolidsThe total area of all outer faces or curved surfaces of a 3D shape, measured in square units and found by unfolding the shape into a net and adding the areas of each piece.
  • Introduction to Systems of Two Linear EquationsA set of two linear equations with the same variables whose solution is the ordered pair that makes both equations true simultaneously, found by locating where their graphs intersect.
  • Measures of CenterA measure of center is a single number that summarizes where the middle or most common part of a data set is located, with the mean, median, and mode being the three most common types.
  • Measures of SpreadA measure of spread describes how much the values in a data set differ from each other and from the center, with range and interquartile range being common examples.
  • Line GraphsA graph that shows how a quantity changes over time by plotting data points in order and connecting them with line segments to reveal trends and patterns.
  • Bar GraphsA graph using rectangular bars to display and compare quantities across separate categories, with bar heights representing values for each category.
  • Simplifying Expressions with the Distributive PropertyThe distributive property allows you to multiply a single number by each term in a group of added or subtracted terms to remove parentheses and combine like terms.
  • HistogramsA graph that organizes numerical data into equal-width intervals called bins and displays the frequency of values in each bin as touching bars to show how data is distributed.
  • Identifying Proportionality from Tables, Graphs, and EquationsA relationship between two quantities is proportional when their ratio stays constant, meaning y equals k times x for some unchanging constant k, and the relationship always passes through the origin.
  • Approximating and Comparing Irrational NumbersIrrational numbers cannot be written as fractions and have non-repeating decimal representations; square roots of non-perfect squares and pi are common examples.
  • Linear versus Nonlinear FunctionsA linear function has a graph that is a straight line with a constant rate of change, while a nonlinear function has a graph that is not a straight line with a rate of change that varies.
  • Scientific NotationScientific notation is a compact form for writing very large or very small numbers as a number between 1 and 10 multiplied by a power of 10.
  • Volume of Three-Dimensional SolidsThe measure of how much space a three-dimensional solid occupies inside, expressed in cubic units.
  • Angles Formed by Parallel Lines and a TransversalWhen a line crosses two parallel lines, it creates eight angles that form predictable pairs with equal or supplementary measures.
  • Applications of the Pythagorean TheoremThe Pythagorean theorem and its converse can be used to find missing sides of right triangles, determine whether a triangle is right-angled, and solve real-world problems.
  • Box Plots and the Five-Number SummaryA five-number summary consists of the minimum, first quartile, median, third quartile, and maximum values from an ordered data set, which are used to construct a box plot.
  • Solving and Graphing Linear InequalitiesA mathematical statement using <, >, ≤, or ≥ to compare expressions and represents infinitely many solutions that can be found and displayed on a number line.

About this course

Welcome to Pre-Algebra

Pre-Algebra is the bridge between the arithmetic you've been doing since elementary school and the more abstract, symbolic thinking you'll use in Algebra I and beyond. Think of this course as a toolkit-building year: you're going to gather and sharpen the tools — numeric fluency, equation-solving skill, graph reading, and geometric reasoning — that Algebra I assumes you already have.

By the time you started this course, you already knew how to work with fractions and decimals, solve simple one-step equations, and handle basic ratios. This course takes those skills much further and adds several brand-new ideas: negative exponents, irrational numbers, functions, transformations, and formal statistics. None of this should feel like a totally different subject — it's a natural extension of what you already know, just with more powerful tools and more precise vocabulary.

Why this course matters

Algebra I assumes you can already:

  • Perform any arithmetic operation on any rational number (positive, negative, fraction, or decimal) without hesitation.
  • Simplify expressions and solve multi-step equations and inequalities involving variables.
  • Read, describe, and reason about relationships shown in tables, graphs, and equations.
  • Apply geometric formulas (area, surface area, volume, the Pythagorean theorem) to solve real problems.
  • Interpret data displays like histograms, scatter plots, and box plots.

If any of these feel shaky, Algebra I becomes a struggle not because the algebra itself is too hard, but because the underlying arithmetic and reasoning skills aren't automatic yet. This course exists to make all of the above second nature.

The six major strands of this course

Pre-Algebra content is usually organized into six connected strands. You won't necessarily study them in strict isolation — many lessons blend ideas from more than one strand — but it helps to know the big categories you're building.

1. The Number System. This strand covers operating with positive and negative rational numbers (integers, fractions, and decimals), understanding order of operations, and classifying numbers as rational or irrational. It also introduces integer exponents (including zero and negative exponents) and scientific notation, which lets you write extremely large or small numbers compactly. This is the arithmetic foundation everything else depends on.

2. Ratios and Proportional Relationships. Here you'll work with ratios, rates, and unit rates, and learn to recognize when two quantities are proportional — meaning they always share the same constant ratio. You'll use this to solve real-world problems involving percents, discounts, markups, simple interest, and scale drawings.

3. Expressions, Equations, and Inequalities. This is the heart of algebraic thinking. You'll learn to simplify expressions using the distributive property and combining like terms, then solve increasingly complex linear equations — including ones with variables on both sides — and linear inequalities. You'll also get an early look at solving systems of two equations.

4. Functions. A function is a rule that assigns exactly one output to every input. You'll learn to represent functions with tables, graphs, equations, and words, and to recognize linear relationships by their constant rate of change (slope). This strand connects numeric patterns to visual graphs, a connection that is central to all of algebra.

5. Geometry. This strand covers angle relationships (like complementary and supplementary angles, and angles formed when a transversal crosses parallel lines), geometric transformations (translations, reflections, rotations, and dilations), congruence and similarity, the Pythagorean theorem, and the surface area and volume of three-dimensional solids like prisms, cylinders, cones, and spheres.

6. Statistics and Probability. You'll learn to summarize data using measures of center (mean, median, mode) and spread (range, interquartile range), and to build and interpret common data displays: histograms, bar graphs, box plots, scatter plots, and line graphs. You'll also study bivariate data — data involving two related variables — and how to describe trends between them.

How the strands connect

These strands are not six separate courses stitched together — they constantly reinforce one another. For example, understanding negative numbers (Number System) is necessary before you can solve equations with negative solutions (Equations). Understanding ratios (Proportional Relationships) sets up your understanding of slope (Functions). Understanding the Pythagorean theorem (Geometry) lets you compute distances that later show up in coordinate geometry and functions. Statistics relies on arithmetic fluency and graph-reading skills built throughout the course.

What success looks like

By the end of this course, you should be able to:

  • Perform any operation on rational or irrational numbers confidently, including with exponents and scientific notation.
  • Simplify and solve multi-step linear equations and inequalities.
  • Recognize and work with proportional relationships and functions in any representation.
  • Apply geometric formulas, including the Pythagorean theorem and volume/surface area formulas, to solve real problems.
  • Construct and interpret the major statistical displays and describe data using measures of center and spread.

This combination of numeric fluency, equation-solving ability, and graph literacy is exactly what you need to walk into Algebra I ready to succeed. Treat this course as your training ground — the habits of precision and step-by-step reasoning you build here will make every future math course easier.

Pre-Algebra: Foundations for Algebra I — Qlaudia