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Let's Investigate Triangles

Vincent and Tara are making triangles with the class construction set. They have a pile of strips of different lengths. How many different triangles can they make?

Seven Sticks

Explore the triangles that can be made with seven sticks of the same length.

Three Fingers and a Loop of String

Using a loop of string stretched around three of your fingers, what different triangles can you make? Draw them and sort them into groups.

Triangle or No Triangle?

Age 5 to 7
Challenge Level
Max from Kiker Elementary School in the United States wrote saying:

This is a square. It has 4 equal sides. It has 4 corners. Each corner is 90 degrees.

Anahita from Guru Gobind Singh Khalsa College in Chigwell told us:

This is a 2-D shape. It has 4 right angles and 4 equal sides. It is known as a square. A right angle is equivalent to 90 degrees.

Nawaf from Pimlico Primary said:

1, 2, 3, 4, 5 are triangles.   6, 7, 8, 9, 10 are not triangles

A triangle has 3 edges and 3 vertices.
For the ones that are not triangles:
One is curved and does not have straight lines
One has a gap in it.
One is not a triangle because it has 4 edges.
The last one is not a triangle because the vertices are not pointy.

Thank you for these solutions. You may be able to find other ways of separating squares from triangles.