What Makes a Shape
Aligned to 1.G.A.1 — Common Core State Standards for Mathematics.
What this lesson teaches
Some things about a shape really matter, like how many sides it has. Other things do not matter, like its color or size.
Worked examples
Example 1
A triangle always has 3 sides. A big red triangle and a small blue triangle are both triangles, because the number of sides is what counts.
Example 2
A closed shape with 4 straight sides is a rectangle whether it is drawn fat, skinny, or tipped on its corner.
Example 3
A shape with a curved, open gap is not a triangle, even if it has 3 corners — a triangle must be closed.
Practice questions
- How many sides does a square have?
- Is a shape still a triangle if we paint it green? Why?
- Name one thing that does NOT change what a shape is.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Qué hace a una figura
Algunas cosas de una figura sí importan, como cuántos lados tiene. Otras cosas no importan, como su color o su tamaño.
Ejemplo 1: Un triángulo siempre tiene 3 lados. Un triángulo rojo grande y uno azul pequeño son los dos triángulos, porque lo que cuenta es el número de lados.
Ejemplo 2: Una figura cerrada con 4 lados rectos es un rectángulo, ya sea gorda, delgada o inclinada sobre una esquina.
Ejemplo 3: Una figura con una abertura curva no es un triángulo, aunque tenga 3 esquinas — un triángulo debe estar cerrado.
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