Sorting Shapes: How Math Groups Things
Look at a box of toy shapes: circles, squares, triangles, and stars. How would you tidy them up? You might put all the ones with 3 corners together, and all the round ones in another pile. That is exactly what mathematicians do. Grouping things by their features is called classification, and it is one of the most useful tools in all of math.
What You'll Learn
You will learn what it means to classify, or sort, shapes into groups. You will learn to name a shape by counting its sides and corners. You will learn how one shape can belong to more than one group at the same time.
Sorting by Sides
A side is a straight edge of a shape. A triangle has 3 sides. A square has 4 sides. A pentagon has 5 sides. When we sort shapes by how many sides they have, a triangle and a pentagon go in different groups, but two triangles go in the same group even if one is big and one is tiny.
Sorting by Corners
A corner, also called a vertex, is where two sides meet. Here is a neat pattern: a flat shape has the same number of corners as sides. A square has 4 sides and 4 corners. A hexagon has 6 sides and 6 corners. A circle is special, it has 0 corners and 0 straight sides, just one smooth curve.
Before you name a shape, count out loud. Touch each corner and say 'one, two, three.' The last number tells you the shape: 3 means triangle, 4 means quadrilateral, 5 means pentagon.
One Shape, Many Groups
A shape can belong to more than one group at once. A square is a 4-sided shape, called a quadrilateral. But it is also a rectangle, because it has 4 square corners. And it is a special rectangle where all 4 sides are equal. So the same square fits into three groups: quadrilateral, rectangle, and square.
Match each shape to its number of sides.
Terms
Definitions
Drag terms onto their definitions, or click a term then click a definition to match.
How many corners does a hexagon have?
Why can a square belong to more than one group?
Build a Shape Sorting Chart
On a big sheet of paper, draw three boxes and label them '3 sides', '4 sides', and 'more than 4 sides'. Cut or draw at least 6 shapes. Count the sides of each one and place it in the correct box. When you finish, tell someone why a square went where it did, and name one shape that belongs to two groups.
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