Shapes and Their Sides
Aligned to 2.G.A.1 — Common Core State Standards for Mathematics.
What this lesson teaches
We name flat shapes by how many sides and corners they have. A triangle has 3 sides, a quadrilateral has 4, a pentagon has 5, and a hexagon has 6.
Worked examples
Example 1
A shape with 4 straight sides and 4 corners is a quadrilateral. A square and a rectangle are both quadrilaterals.
Example 2
A stop sign has 8 straight sides and 8 corners, so it is an octagon.
Example 3
Count sides, not colors. A small green pentagon and a huge yellow pentagon are both pentagons because both have 5 sides.
Practice questions
- How many sides does a triangle have?
- What do we call a shape with 6 sides?
- Draw a shape with 4 sides and name it.
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
Las figuras y sus lados
Nombramos las figuras planas por cuántos lados y esquinas tienen. Un triángulo tiene 3 lados, un cuadrilátero tiene 4, un pentágono tiene 5 y un hexágono tiene 6.
Ejemplo 1: Una figura con 4 lados rectos y 4 esquinas es un cuadrilátero. Un cuadrado y un rectángulo son cuadriláteros.
Ejemplo 2: Una señal de alto tiene 8 lados rectos y 8 esquinas, así que es un octágono.
Ejemplo 3: Cuenta lados, no colores. Un pentágono verde pequeño y uno amarillo enorme son pentágonos porque los dos tienen 5 lados.
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