together flat shapes, such as squares and triangles. One shape they made was a fivesided pyramid made of five same-sized equilateral triangles. The bottom of such a shape is a pentagon! To get their...
The special triangle
Thousands of years ago, in ancient Egypt, there were men known as "rope-stretchers." It was their job to mark out the boundaries of fields and the foundations for houses, temples, and palaces. The...
A square puzzle
Long ago, there was a farmer whose land was in the shape of a square. Each side of the square was exactly one hundred paces long. One day, a tired, dusty man knocked on the farmer's door and asked...
Counting triangles
The design shown above is made entirely of triangles. How many triangles, of all sizes, do you think there are? Altogether, there are 88 triangles! See if you can find them all. There are 42...
Triangle tricks
Triangles are tricky shapes. You can do some surprising things with them. Let's make a triangle that you can do some tricks with. You'll need a piece of paper about the size of this book, and a...
A triangular tale
A triangle called Isosceles, And his friend who was known as Obtuse, Were arguing over the very best way To cook a Christmas goose. "Let's bake it," the Obtuse one said, "In an open fireplace,...
Meet the triangle family
Every angle has one side that is open. If you close this open side, you'll have a closed shape with three straight sides and three angles. A shape of this kind is called a triangle ang guhl)....
Meet the angle family
People have names. And we give names to different kinds of animals. So why shouldn't angles have names? They do! Angles are named after the kind of corner they make. An angle that forms a square...
Dot-picture shapes.
You've probably made dot pictures lots of times. They're pictures you make by drawing lines from one dot to another. Well, here are some special dot pictures you can make for yourself. Get a paper...
Points and lines
What is this • ? You probably said, "It's a dot." Or maybe you said, "It's a period." Well, it could be a dot or a period. But to mathematicians, it's a picture of a point. You probably think of a...