These discussions are designed to give teachers ideas for how to introduce or explain a concept with a student or with a class. Informal and formal definitions of concepts are given. Common student misconceptions are pointed out as well. Teachers might have students read them or, more commonly, use ideas from them to guide class discussions. They are arranged according to the NCTM Principles and Standards for School Mathematics.

Number and Operation Concepts: Includes working with fractions and decimals, clock arithmetic, and finding number patterns. (NCTM Content Standard)

Geometry and Measurement Concepts: Includes basic notions of lines, rays and planes, working with tessellations, fractals. (NCTM Content Standard)

Function and Algebra Concepts: Includes an introduction to functions, special properties of linear functions, graphs and the coordinate plane, and reading graphs. (NCTM Content Standard)

Probability and Data Analysis Concepts: Includes an introduction to probability, conditional probability, sampling, expected value, statistics, histograms, boxplots, and the normal curve. Also includes statistical simulations. (NCTM Content Standard)

These discussions are best accessed from the lessons in which they are used, but are listed here for convenience. Teachers who develop discussions similar to these for other topics are encouraged to submit them to the Project Interactivate archives. Contact the Interactivate Project Team for details.



Number and Operation Concepts


Fractions Discusses the introductory concept of a fraction.
Comparing Fractions Introduces students to the basics of reducing fractions and learning to identify which of two fractions is larger or smaller.
Decimals Deals with converting fractions into decimals.
Multiplying Decimals and Mixed Numbers A review of the definition of decimals and mixed numbers as well as a description of multiplying decimal numbers.
Percents Covers the basics of converting fractions into percents.
Fraction Adding and Subtracting Demonstrates how fractions are added and subtracted.
Fraction Multiplying and Dividing Explains multiplication and division of fractions.
Sets and Elements Gives an introduction to sets and elements.
Venn Diagrams Introduces Venn Diagrams.
What are Multiples? Reviews multiplication of integers as repeated addition.
What are Remainders? Reviews long division of integers and modular arithmetic.
Clocks and Modular Arithmetic Shows how modular arithmetic can be thought of as clock arithmetic.
Cryptography and Ciphers Introduces the notion of using modular arithmetic to encode messages.
Infinity and Iteration Discusses infinity and repeating processes infinitely many times
Recursion Discusses recursion from the point of view of fractals
Exponents and Logarithms Gives an introduction to logs, needed for calculating fractal dimension


Geometry and Measurement Concepts


Quadrilaterals Introduces students to quadrilaterals and defines the characteristics of the polygon.
Parallelograms Introduces students to parallelograms and rombuses and defines the characteristics necessary to determine each shape.
Rectangles Introduces students to rectangles and squares and defines the characteristics necessary to determine each shape.
Trapezoids Introduces students to trapezoids and isosceles trapezoids and defines the characteristics necessary to determine each shape.
What are Tessellations? Examines the properties of tessellations.
Tessellations in the World Looks at the history of Tessellations, why they are important and examines some patterns in nature and art.
Symmetry in Tessellations Defines symmetry and demonstrates different types of plane symmetry.
Color in Tessellations Explains the effect that color has on the patterns we see in tessellations.
Optical Illusions Examines optical illusions.
Shape Explorer Introduces students to finding areas and perimeters of irregular shapes.
Lines, Rays, and Planes Introduces students to lines, rays, line segments, and planes.
Translations, Reflections, and Rotations Introduces students to the concepts of transformations.
Surface Area and Volume Introduces students to the concepts of surface area and volume.
Self-Similarity Discusses self-similarity from the point of view of fractals
Plane Figure Fractals Compares line bending fractals to plane figure fractals
Properties of Fractals Discusses fractal properties and fractal dimension
Dimension and Scale Discusses what dimension is and how it is related to scale, giving the relationship needed to calculate fractal dimension
Chaos Introduces the notion of chaos as the breakdown in predictability
Chaos is Everywhere Mentions the wide spread use of fractals and chaos in science
Pascal's Triangle Introduces Pascal's Triangle
Dimension for Irregular Fractals Looks at random fractals and how self-similarity is generalized
Prisoners and Escapees -- Julia Sets Looks at iterating functions and starting points that stay close versus go off to infinity.
The Mandelbrot Set Shows how Julia sets for functions (a,b)^2 + (c,d) are used to make the classic Mandelbrot set.


Function and Algebra Concepts


Functions as Processes or Rules "Function machines" discussion
More Complicated Functions "Composite function machines" discussion
Linear Functions "Linear Function machines" discussion
Introduction to the Coordinate Plane and Coordinates First introduction to coordinates
From Graphs to Machines and Back Graphing and function rules: first connections
Functions and the Vertical Line Test The verical line test for functions
Gathering Information from Graphs From graphs to stories
Graphing Time, Distance, Velocity and Acceleration Analyzing graphs and building new graphs from old ones
Impossible Graphs What makes a graph impossible and how to avoid these problems

Two-Variable Functions Introduces two-variable functions of the form (a,b)^2 + (c,d)


Statistics and Probability Concepts


Polyhedra Questions about dice lead to discussion of polyhedra
Fair Choice What does it mean exactly to play fair or to choose fair?
Random Number Generators What methods are there for random (fair) choice between several numbers?
Probability and Outcome Introduction and initial discussion of the concept of probability
Events and Set Operations Introduction of elementary set operations and their connections with probability
Tables and Combinatorics Discussion of tables as a convenient way to store and count outcomes
Divisibility The question of fairness in a two dice game leads to divisibility discussion
Trees as Data Structures Questions about games with more than two dice lead to discussion of trees as another kind of data structure
Stem-and-Leaf Plots Introduces Stem-and-Leaf Plots to students.
Probability of Simultaneous Events Computing exact probabilities for the Racing Game leads to the formula for the probability of simultaneous events
Expected Value Introduction and discussion of the concept of expected value
Probability and Geometry From counting chances to measuring proportions of areas
Conditional Probability Introduction of the concept of conditional probability and discussion of its application for problem solving
Replacement Extends the notion of conditional probability by discussing the effects of replacement on drawing multiple objects
Think and Check! Some problems are tricky; probability theory provides unique ways to check the solutions
Internet Search and Set Operations Introduction of elementary set operations through internet searching
Probability vs. Statistics Definitions of statistics and probability. Comparing and contrasting probability and statistics
Mean, Median, and Mode Mean, median, and mode
The Normal Distribution and the Bell Curve An introduction to both the normal distribution and the debate over the 1994 book
"The Bell Curve" revisited Finishes up the discussion of the book as well as exploring individual differences versus group expected values
Continuous Distributions Discusses continuous versus discrete distributions
Class Interval: Scale and Impression How scales help to represent or mis-represent data in histograms
Vertical Scale: Increase or Decrease? Class interval size influences the look and interpretation of histograms
Histograms vs. Bar Graphs Differences and similarities

Box Plots How to build box plots, including medians and quartiles


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