Make new shapes from triangles: a 1st grade geometry activity
What it is: a 1st grade geometry activity where students fold and cut paper squares into triangles and put the triangles together to make new shapes: a bigger triangle, a square, a rectangle and a parallelogram. Students learn that shapes can be built from other shapes.
Time: about 25 minutes. Grade: 1st grade.
Materials: 3 paper squares per student, safety scissors, glue sticks, and paper for recording.
- Fold a square corner to corner and cut on the fold. Ask: "What two shapes did we make?"
- Students cut their squares into 6 triangles.
- Challenge: "Use 2 triangles to make a square again. Now make a bigger triangle."
- Next: "Use 4 triangles to make a rectangle." Then try a slanted shape (a parallelogram).
- Students glue their favorite new shape on paper and write how many triangles they used.
Safety: use safety scissors and model how to pass and hold them.
Differentiation: students who need support get pre-cut triangles. Students who are ready try to make a trapezoid with 3 triangles. English learners can use a shape poster to name their shapes.
Quick check: show two triangles and ask a student what shapes they could make by putting them together.
Save this activity to your library so it is ready when you need it.
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About this resource
- Shared by
- @UpOnlyLearning · Curriculum team
- Posted
- Oct 29, 2026
- Type
- Lesson plan
- Grade
- Grades K–2
- Subject
- Math
- Language
- English
- License
- Free for classroom, co-op and tutoring use. Please don't resell.