Virtual Lesson: Geometry I

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Types of Triangles

  • There are three types of triangles.
  • Each type has 3 sides, 3 angles (created by two sides) and 3 vertices (the point where 2 sides meet).
  • Each type will be created using straws and string then labeled.

Materials: Straws, string, scissors, paper, pencil

Please read about straws at the end of the blog.

There are 3 types of triangles to make.

  • Equilateral Triangle
  • Isosceles Triangle
  • Scalene Triangle

Make each triangle with straws

Equilateral Triangle: Read the instructions before you begin.

  1. Cut three straws the same length using the same color.
  2. Unwind the amount of string you think you will need. Do not cut the string. Push the string into the 3 straws.
  3. Lay the work flat and form the triangle.
  4. Make sure you have enough string on both ends to make knots.
  5. Cut the string and tie three knots.
  • Isosceles Triangle: Read the instructions before you begin.
  1. Cut 2 straws the same length using the same color.
  2. Cut 1 straw that is shorter in length and choose a different color.
  3. Follow instructions 2, 3, 4, & 5 above.
  • Scalene Triangle Read the instructions before you begin.
  1. Cut 3 straws in 3 different lengths using three different colors.
    • one long, one medium, and one short.
  2. Follow instructions 2, 3, 4, & 5 for the Equilateral triangle.

Record your work.

  • Make one large title label for the whole work. Kinds of Triangles
  • Make a name label for each kind of triangle.
    • Equilateral Triangle, Isosceles Triangle, Scalene Triangle
  • Place the name next to the triangle or above it.
  • Place the title above the 3 names and triangles
  • Have your work checked.


  • Spelling words to master: type, triangle, sides, angles, vertex, vertices, equilateral, isosceles, scalene
  • Make a Sorting Game.
    • Make 1-3 small triangles, 1-3 large triangles and 1-3 medium size triangles of each type. Small could be described as tiny, medium as average, and large as the biggest one that can be made with the straws available.
    • Choose a level of difficulty for your game.
      • To make it easy to sort, use one color of straws to make all the triangles of one kind (the small, medium and large). The color of each is a clue.
      • To make it more difficult to sort, use a different color of straws for each size (the small, medium and large) of each kind of triangle. The color is not a clue.
      • To make it very difficult to sort, use a different color for each side of each type of triangle and for each different size.
    • Put 3 straws on a string and make one knot. If you like it, tie 3 knots and trim off the string. If not, open the knot and try again.
    • Set up the labels like you did to have your work checked.
      • Put plenty of space between the names of the triangles. A lot of space will be needed for sorting.
    • Place the examples you made under the correct name.
    • Mix up all of your sorting triangles and put them on a tray, in a basket, or just pile them up to the left of the labels and examples.
    • Invite your family to sort the triangles.
    • Check their work.
    • Invite the family to check the work with you. Correct each type separately so that each triangle gets placed with those it matches.
  • Decide what to do with your triangles.
    • Cut them all apart and use the straws to build Polyhedrons.
      • Go to
      • Click on curriculum, click on Art Forms II, click on Polyhedrons. Scroll through the lessons and choose.
    • Store the straws in a plastic bag to be creatively used later.
    • Cut the straw into little pieces and put them on a string to make a necklace. When it is long enough to put over your head cut the string and make 3 knots and trim.

 Note: If you are throwing the straws away, cut the straws into little pieces. That   way animals, especially birds, will not get hurt if they find them.

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