Serving advanced learners (and their teachers) since 2012.

Arizona Math Standard: 4.G.A.2

Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size (e.g., understand right triangles as a category, and identify right triangles).

What’s In My Brain: H vs Arrow
What’s In My Brain: H vs Arrow
Two columns. One is an example, one isn’t. Can you figure out the hidden rule before the big reveal?
Gr 1, 2, 3, 4, 5, 8
What’s In My Brain: Pentagon vs Pentagon
What’s In My Brain: Pentagon vs Pentagon
We’re looking at regular vs irregular polygons.
Gr 1-8
Grouping Shapes by Parallel and Perpendicular Sides
Grouping Shapes by Parallel and Perpendicular Sides
Which shapes go together based on parallel and perpendicular lines?
Gr 1, 2, 3, 4, 5, 8
Letters With Symmetry
Letters With Symmetry
Let’s group letters by their symmetry, then create symmetrical words, and then symmetrical sentences!
Gr 3, 4, 5, 6, 8
Crossing Every Bridge Exactly Once (aka Eulerian Paths)
Crossing Every Bridge Exactly Once (aka Eulerian Paths)
How can you cross each bridge in this city exactly once?
Gr 2-4
Geometry Image: Esplanade Theaters
Geometry Image: Esplanade Theaters
What odd and interesting shapes can your students find in this geometric image?
Gr 1, 2, 3, 4, 5, 8
Geometry Image: University Ave
Geometry Image: University Ave
What odd and interesting shapes can your students find in this geometric image?
Gr 1-5
Geometry Image: Victoria Conference Center
Geometry Image: Victoria Conference Center
What odd and interesting shapes can your students find in this geometric image?
Gr 1-5
Geometry Image: Skytree
Geometry Image: Skytree
What odd and interesting shapes can your students find in this geometric image?
Gr 1, 2, 3, 4, 5, 7, 8
Geometry Image: Steigerwald
Geometry Image: Steigerwald
What odd and interesting shapes can your students find in this geometric image?
Gr 1, 2, 3, 4, 5, 7
Math Curiosity: Klauber’s Triangle
Math Curiosity: Klauber’s Triangle
In 1932, a leading authority on rattlesnakes, Laurence Klauber, discovered a startling pattern within a triangle of primes.
Gr 1-5
Math Curiosity: Ulam Spiral
Math Curiosity: Ulam Spiral
What if we make a huge spiral of numbers and then highlight only the primes? Well, a bunch of weird patterns show up!
Gr 1-4
What’s In My Brain: Trapezoids or Not?
What’s In My Brain: Trapezoids or Not?
Which are trapezoids and which are not?
Gr 1-8
Intersecting Angles and Streets
Intersecting Angles and Streets
There can never be just one angle.
Gr 1, 2, 3, 4, 7, 8
Math Curiosity: The Coloring Problem
Math Curiosity: The Coloring Problem
No video gets me more email from students! How few colors can you use to color in any map so that no two, neighboring regions are the same color?
Gr 1
The Angles of a Triangle
The Angles of a Triangle
Why tell a kid the rules of a triangle when they can discover them!?
Gr 1, 2, 3, 4, 5, 7, 8
Grouping Quadrilaterals In A Hierarchy
Grouping Quadrilaterals In A Hierarchy
Can we classify quadrilaterals like we classify living things?
Gr 1-5