### A Hindu Algebra Problem

This problem is typical of the earliest algebra problems that likely came out of India. It is interesting historically, and it is the kind of problem students are still taught … Read more

### Absolute Value Functions

The absolute value (ABS) function is the positive value of a number or quantity. Its graph has a very peculiar shape, a V. Since absolute values are always positive we … Read more

### Absolute Value Polynomials

What would you guess the absolute value of a polynomial function would look like? Try some here. I think you will be very surprised. Can you explain what you see?

### Adding Machine

Multiplication is often thought of as repeated addition. By building a times table by using a repeated addition rule you will have a fun practice of the multiplication facts, and … Read more

### Addition Patterns

Now that students can build addition tables, they should look for the patterns in them. We introduce them to a variety of things they might want to look for. We … Read more

### Addition Table

From here on students can go in most any order they choose. They can start with addition or with multiplication. They should imagine themselves on an elevator able to go … Read more

### Addressing

We have been using cell addresses informally until now, but now we can be more formal and explicit. Different spreadsheets have different types of address bars, but all use the … Read more

### Air Pollution

This chart recently came out from the American Lung Association about air pollution in the United States. How would you present this data to Congress to get them to deal … Read more

### Associativity

Parentheses are not only important in paper math, they are critical in spreadsheets. To make sure that terms are handled properly by spreadsheets, we have to be sure we use … Read more

### Battleship

Spreadsheets can be a great place for you to build your own games. Ryan has built one of his early favorites, Battleship, where you learn graphing as you try to … Read more

### Build a House

Spreadsheets with their natural grid make a great, though not entirely flexible, platform for architectural design and for working with shapes. Build a house introduces students to using spreadsheets to … Read more

### Build a Times Table

Students are tasked to build a times table in just two steps. They have to learn to use absolute as well as relative addressing to do, and the Lab takes … Read more

### CO2 Growth

Spreadsheets offer us a nearly unlimited ability to develop and learn from case studies using real world data. We will focus mainly on climate change which is an area rich … Read more

### Coffee Money

Are you a coffee drinker? Small daily expenses like coffee can quickly add up. By using spreadsheets to organize cost, you can monitor how much you’re really spending.

### Common Denominators

We can use these proportions to compare two ratios with different denominators by finding a denominator that their proportions have in common. Thus the common denominator of 2/3 and 3/4 … Read more

### Commutativity

The symmetry of the multiplication table around the square numbers diagonal we call commutativity or the commutative property. It means that in a 12 by 12 multiplication table we need … Read more

### Composition of Functions

One of the most powerful aspects of the mathematics of functions is our ability to treat them as abstract quantities (essentially numbers) and then combine them with standard operations. But … Read more

### Counting By

Counting-By introduces multiplication. Counting-by or skip-counting is, we believe, the best way to help students build their multiplication facts, and though they will live in an age of ubiquitous spreadsheets … Read more

### Credit Cards

How much are your credit cards costing you? If you are like most of us, they are very expensive because we have credit card debt. This Lab will help you … Read more

### Decimal Addition

Decimal addition is one of a series of Labs to help you understand and learn to use decimals. I think you will find it fun because it uses random numbers … Read more

### Decimal Division

Decimal Division is one of a series of Labs to help you understand and learn to use decimals. I think you will find it fun because it uses random numbers … Read more

### Decimal Multiplication

Decimal Multiplication is one of a series of Labs to help you understand and learn to use decimals. I think you will find it fun because it uses random numbers … Read more

### Decimal Subtraction

Decimal subtraction is one of a series of Labs to help you understand and learn to use decimals. I think you will find it fun because it uses random numbers … Read more

### Decimals and Percents

Ratios can be written in a wide variety of different way: as fractions, as decimals, and as percents.,with a colon, with a slash, as a fraction and even as a … Read more

### Distributivity

The distributive property turns out to be central to a surprising variety of important mathematics. One of the most valuable is to use it to break products into two pieces … Read more

### Division and Ratio

We can make a division table just like we made a multiplication table. Spreadsheets will usually turn such tables into decimal quotients. Excel will allow you to see these quotients … Read more

### Drawing Triangles

Though spreadsheets lets you put geometric shapes on the screen, those shapes are not connected with the cells and cannot be changed by using different values. We wanted to make … Read more

### Enigma Machine

Spreadsheets are great for creating secret codes and for breaking them. During World War II the German military used a machine they called Enigma to send coded messages. In a … Read more

### Equivalent Fractions

Fractions are ratios that’s why we call them rational numbers (ratio numbers). If you think about fractions as ratios, how does this help you to understand them?

### Exploring Triangles

Create, manipulate, and explore triangles in this live interactive spreadsheet. On the surface, a triangle is being drawn on a graph, but the real magic lies in the formulas used … Read more

### Exponential Functions

What if you created a function where the exponent is a variable? As you might expect, this would be called an exponential function. When you hear someone talk about “growing … Read more

### Factor Pairs

Multiplying creates products, factoring separates a product into the numbers that make it up. We thus start with the table and then look at the axes to find the factor … Read more

### Factor Table

Spreadsheets always automatically perform the operations you ask them to do. But sometimes we want to see the process. We can make spreadsheets show us that in several ways. Here … Read more

### Fibonacci’s Sequence

Fibonacci, the nickname given the great medieval mathematician Leonardo of Pisa, is connected in most of our minds with the Fibonacci sequence. Spreadsheets make wonderful tools for creating such sequences. … Read more

### Gas Money

If you commute to work or school, you understand how expensive driving can be. Choose a car in this interactive spreadsheet as it breaks down the cost of driving, using … Read more

### Graphing

Graphs as we know them were first invented by Galileo. They are powerful images of functions. I will introduce you to graphs by letting you graph different functions represented by … Read more

### Hit Streak

In 1941, Joe DiMaggio got a hit in 56 straight games. This record has never been beaten. Some say it is the greatest record in all of sports. You can … Read more

### How Many Times

How many of the numbers from 1 to 100 are in the times table? All, Most, Less than half? I think you will find in this exploration of the relationship … Read more

### Hundreds Table Patterns

We introduce students to more complex patterns and rules in hundreds tables. In particular, we have students look at diagonal patterns and develop rules to fill them. This spreadsheet hundreds … Read more

### Interest

Which form of interest, simple or compound, is the fairest? If you were buying a house or a car which would you rather have, which would you consider fair? Or … Read more

### Introducing Spreadsheets

In introducing Spreadsheets we want you to learn to build a numberline by using a rule (a formula). We begin with a simple rule that you can copy and paste into the entire … Read more

### Introducing Subtraction

What if you built a rule that would enable you to count backwards? How would it be the opposite of addition? What would happen if it goes past zero?

### Inverse Functions

What does a function look like when we interchange the inputs and outputs, that is make the x-axis the y-axis and vice versa.

### Inverse of a Function

Spreadsheets make it very easy to switch axes and add graphs. They enable students to play with what may have been difficult and abstract concepts like the inverse of a … Read more

### Lease or Buy

If you are in the market for a new car, you often have a decision to make. Do you want to buy the car or lease it. I have, over … Read more

### Lemonade Stand

Manage a business. The Lemonade Stand has been a business simulation developed in many different versions. We believe this is the first time that it has been created as a spreadsheet simulation. … Read more

### Lights Out

This is one of those math puzzles that come up in contests but which turn out to be quite interesting mathematically. Imagine a long hallway with lights in the ceiling, … Read more

### Linear Functions

Linear functions are the most important family of functions. They pervade our everyday lives and our work. Their graph is a line, and their general form is f(x)=mx+b where m … Read more

### Lissajous Figures

We often see Lissajous figures in old sci-fi movies because they are so cool. As you play with them I think you will find them as fascinating as I do. … Read more

### Make a Hundreds Table

This is the graduation exercise for the basic use of spreadsheets. We combine rules and addressing to have students build their own hundreds table in the fewest steps. There are … Read more

### Making Fractions

Spreadsheet math generally focuses on ratio and proportion to develop the concept of fraction. But fractions is such a big problem in today’s curriculum that it seemed only right to … Read more

### Margin vs Markup

How should you figure out your profit? If you have an item that you are selling, should you price it at 25% over its cost to you, or should you … Read more

### Mixture Problems

How many gallons of a 70% alcohol solution must be added to 30 gallons of a 10% alcohol solution in order to produce a new mixture, a 20% alcohol solution?

### Moore’s Law

It was one of the most amazing visions of the future ever made. In 1965 Gordon Moore, one of the founders of Intel, proposed a law governing the future of … Read more

### More Number Lines

We use rules to build new numberlines. For example we can start in the middle and go both forward or backward using adding and subtracting rules. You can even generate and experiment with negative numbers … Read more

### Motion Problems

George is in New York and Martha is in Washington. They leave at the same time and follow the same road to meet each other on the way. The distance … Read more

### Multiplying Integers

We have made a big deal of the times table and of other tables.Now we extend the times table to negative numbers and thus to all 4 quadrants of the … Read more

### Napoleon’s Pyramid

When Napoleon conquered Egypt in 1798 he went to the Great Pyramid of Giza. While his men climbed to its peak, he figured out that “There is stone enough to … Read more

### Normal Distribution

Most museums with math exhibits have a Pascal’s triangle made up of pegs with balls falling down between them and bouncing off of them. One of the things they want … Read more

### Number Lines

Number Lines introduce students to functional thinking and the use of formulas in spreadsheets. For younger students we call these formulas “rules” and ask students to build a variety of … Read more

### Number Patterns

Use numberlines and spreadsheet rules to explore the amazing patterns we find in our whole numbers. Did you know that you can get the odd numbers by subtracting the square … Read more

### Number Series

Spreadsheets make it easy for us to explore patterns in the whole numbers. This Lab does that and helps you learn the basics of spreadsheets like cell addressing, copy and … Read more

### Odd Times

How many of the products in a 12 by 12 times table are odd numbers? This is a question we rarely ask in paper-based math classrooms, yet it is an … Read more

### Parentheses and Pi

Parentheses are very important in spreadsheets because like all programming, spreadsheet formulas have to be very specific. A big formula, especially one like Viete’s approximation of pi, likely will require … Read more

### Pascal’s Triangle

Another famous pattern, Pascal’s triangle, is easy to construct and explore on spreadsheets. Create a formula for any cell that adds the two cells in a row (horizontal) above it. … Read more

### Pennies to Heaven

Pennies to Heaven is a Fermi Problem, basically a “headmath” experiment. Fermi Problems, originally developed by Enrico Fermi, one of the greatest experimental and theoretical physicists of the 20th century, … Read more

### Personal Budget

How much money do you spend? How much money can you save? We all need to know these things, but you can’t know them until you build and track a … Read more

### Peter’s Taxi

There are a wide variety of financial literacy problems. This is the kind of problem that appears on many tests. It does not ask you directly to find the cost … Read more

### Phone

Use spreadsheets to compare popular phone carriers and the plans they offer.

### Place Value

Our number system inherited from India and from the Medieval Arab world enables us to use just 10 symbols to write any number we can imagine. Students learn in this … Read more

### Place Value: Decimals

We take our place value generator to decimals to help students see the simplicity of the place value pattern going right as well as left.

### Place Value: Thousands

We extend the place value generator to 100’s of thousands to show you how the pattern of 1’s, 10’s, 100’s, continues to 1,000’s, 10,000’s, 100,000’s. Enter numbers and watch the … Read more

### Polynomial Functions

Polynomial functions are not limited to the highest term and while that term is most important in determining the shape of its graph, additional terms play a role. Try out … Read more

### Power Functions

Adding an exponent, sometimes referred to as a ‘power’, to the input variable of a linear function that passes through the origin creates a power function. Changing the parameters of … Read more

### Powerball

You just won the Lottery worth $600,000,000. You have a choice between taking it as a lump sum of $376.9 million or in yearly payments of $20,000,000/year for 30 years. … Read more

### Powers of Ten

Picturing exponential growth, powers of 10, can be hard for any of us to imagine. The spreadsheet has the flexibility to enable us to explore the powers of 10 and to … Read more

### Prime Numbers

The prime numbers are among the most fascinating objects in all of mathematics. While we can generate them, we do not know or understand their pattern. Yet, they have some … Read more

### Probability: Flipping a Coin

That probability is multiplicative is not an easy concept for many of us. Using the spreadsheet with our ability to make tables and to cut and paste can make this … Read more

### Products as Areas

Using the times table, students can see that products are always rectangles, and that they represent the area of that rectangle. They should explore the times table by playing with … Read more

### Projectile Motion

Let’s do a little target practice with this spreadsheet projectile simulator, which will map out the flight path of an arrow shooting toward a target.

### Quadratic Functions

What does each of the coefficients do? How does it change the graph of the parabola. What does a do, what does c do and a question still rarely asked, … Read more

### Rate of Growth

We look at world population over the past 60+ years and ask whether the earth’s population is growing faster or slower today. Is it out of control and something we … Read more

### Ratio and Proportion

We think about ratio tables in terms of motion. Move up 2 and over 1, or move up 1 and over 2. In this way we build proportional patterns. By … Read more

### Rows and Columns

We use the hundreds table to introduce rows and columns and focus students on seeing the patterns in these tables. Again and again we go back to making rules and … Read more

### Rule of 72

The rule of 72 is an old banker’s rule of thumb to find out how long it will take to double your money at different interest rates. Financial literacy has … Read more

### Sierpinski Fractals

Fractals are a new 21st century mathematics. They are patterns that repeat themselves at various scales. This one is based on the odd numbers in Pascal’s triangle. We learn to … Read more

### Similar Triangles

Scatterplot graphs enable us to build shapes using spreadsheets and to practice transformational geometry. They are surprisingly flexible tools. And since they depend upon a table of value and that … Read more

### Sine Function

Spreadsheets are not limited to algebraic functions, they can also display trigonometric functions. We are modeling the sine function, but you can try any of the trig functions by going … Read more

### Solving Equations

Typical algebra courses start with equations and solving equations and then move to graphing and functions. We start with functions and use them to solve equations. We treat an equation … Read more

### Solving Equations Digitally

This lab introduces a method for solving or estimating the solution to an equation digitally that can be applied to many types of equations. This Functional Thinking approach reduces the … Read more

### String Challenge

Strings need not begin and end on axes that are at right angles to each other which we call Cartesian. It is quite interesting that Descartes himself did not use … Read more

### String Diagrams

The usual way to make string diagrams using rubber bands or yarn on a board with nails does not allow much exploration. Mary Boole meant them as exercises in visualization. … Read more

### Subtraction Tables

What would a subtraction table look like? How would its pattern be different from an addition or multiplication table? Is subtraction commutative?

### Sudoku Challenge

Have you ever played Sudoku? It is fun and challenging. You have to find the numbers from 1 to 9 in each cell so that that all of the numbers … Read more

### Syracuse Problem

I built a Lab for you to play with the Syracuse Problem and to learn to use spreadsheets to play with like problems in fun and interesting ways. The Syracuse … Read more

### Systems of Equations

Solving systems of equations sometimes called simultaneous equations with graphs is simply a matter of finding out where they intersect. One of the most valuable things students can learn is … Read more

### The Chessboard

We take that great old problem of the inventor of chess and the ruler of India and use it to see how powers of 2 grow in size. We start … Read more

### The Magic Rectangle

Multiplication tables have some wonderful and quite surprising patterns. This is one of them. Draw any rectangle in a multiplication table and you will find that the products of opposite … Read more

### The Square Numbers

The square numbers form an interesting pattern on the times (multiplication) table. They run along a diagonal from 1 to the top right of the table separating the table into … Read more

### Triangular Numbers

1, 3, 6, 10… are called the triangular numbers because they can be stacked up to form a triangle. They are very interesting numbers, and they form a very interesting … Read more

### What is x?

What is “x”? Or how do we represent variables and functions on spreadsheets? Download What is x?

### Work Problems

Suppose Tom can paint the entire fence in twelve hours, and Huck takes eight hours. How long would it take the two of them together to paint the fence?