Pentagram Triangles

How many triangles are formed?

Magic Triangle

Place the digits 1 through 9 in the circles in a very special way.

Counting Triangles

Determine the number of triangles in the diagram.

Non-Overlapping Triangles

Use three lines to form as many triangles as possible.

Lining Up to Find Triangles

Draw lines to find the largest amount of triangles.

Toothpick Transfer

Readjust a diagram to form a number of triangles.

Hidden Triangles

Count the number of triangles in a picture.


Explore Symmetry with Altitudes and Medians.

Triangular Numbers

Explore the sequence of triangular numbers.

Triangles Inscribed Inside Triangles

Explore properties of triangles constructed using the midpoint of given triangles.

Constructing Isosceles Triangles

Explain how to construct isosceles triangles.


Tile a square patio with triangular tiles.

Slicing Triangles

Cut any given triangle into triangles of equal area.

Prime Scalene

Find the smallest possible perimeter of a scalene triangle.

Triangles Inside a Trapezoid

Use the area of a triangle to transform a trapezoid into different quadrilaterals.

Area Formulas

Investigate the areas of triangles in a variety of ways.

Interactive Pythagoras

Use the concept of area to demonstrate the Pythagorean Theorem.

Planting Trees

Help a farmer plant four trees.

Half As Much May Be Right

Explore triangles inscribed in semicircles.

Balancing the Triangular Totter

Locate the center of mass of a triangle.

To Be or Not to Be

Determine the necessary conditions to create a triangle.

Outside Looking In

Identify the sum of the exterior angles in a triangle.

Remotely Interior

Compare exterior angles with remote interior angles.

Shark Attack!

Find the best path from the inside of a triangle to its sides.

Sum It Up!

Explore the sum of interior angles of a triangle.

Classified Information

Investigate combining triangle classifications based on length and angle measure.

In or Out?

Determine the location of the altitudes in a triangle.