# Ratios

### 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… Continue

### Birthday

In a class of 23 students, the chances are fifty-fifty that two of them will have the same birthday. Now that may sound impossible since… Continue

### 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… Continue

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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### Division and Ratio

We can make a division table just like we made a multiplication table. Division is surprisingly our most important operation in terms of most of… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### Magic Number (Infinite Series)

What if you made a series of unit fractions with the odd numbers as their denominator, added the first two together, subtracted the next one,… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### 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… Continue

### Shapes

Shapes introduces student to changing the colors in cells and to changing the shapes of cells by dragging the column or row separators in the… Continue

### Solar System

When I was young I loved to play with planetary data, to explore their patterns, to learn more about astronomy, and to deal with large… Continue

### 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… Continue

### 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… Continue

### 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… Continue