Curated OER
Peter's String
Students are introduced to the math problem and consider how they could approach it. In pairs, students investigate Peter's conjecture in any way they see fit. They then share their answers with the class.
Texas Instruments
Texas Instruments: Properties of Parallelograms
In this activity, students go through the process of proving a quadrilateral to be a parallelogram. They understand the various characteristics of a parallelogram.
CK-12 Foundation
Ck 12: Geometry: Quadrilaterals That Are Parallelograms
[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to prove that a quadrilateral is a parallelogram given the properties of parallelograms.
CK-12 Foundation
Ck 12: Geometry: Quadrilaterals That Are Parallelograms
[Free Registration/Login may be required to access all resource tools.] Prove a quadrilateral is a parallelogram.
Illustrative Mathematics
Illustrative Mathematics: G Co, G Srt Congruence of Parallelograms
In this task, a student has learned the SSS and SAS congruence tests for triangles and wonders if these tests might work for parallelograms. Aligns with G-CO.C.11 and G-SRT.B.5
Illustrative Mathematics
Illustrative Mathematics: G Co Is This a Parallelogram?
In the pictured quadrilateral, opposite sides are congruent and young scholars must explain whether this makes it a parallelogram. Aligns with G-CO.C.11.
Maths Challenge
Maths challenge.net: Quadrilateral Parallelogram
A "three star geometry problem" requiring knowledge of how to complete geometric proofs and some prior math knowledge. This problem asks to prove that the mid points of any quadrilateral form a parallelogram.
Texas Education Agency
Texas Gateway: Making Conjectures About Quadrilaterals
Given examples of quadrilaterals and their component parts, the student will use explorations and concrete models to prove a quadrilateral is a parallelogram, rectangle, square, or rhombus using opposite sides, opposite angles, or...
Illustrative Mathematics
Illustrative Mathematics: G Co Midpoints of the Sides of a Paralellogram
Suppose that ABCD is a parallelogram and that M and N are the midpoints of lines AB and CD respectively. Students are asked to prove that MN=AD, and that the line MN is parallel to line AD. Aligns with G-CO.C.11.
CK-12 Foundation
Ck 12: Interactive Geometry: 4.7 Theorems About Quadrilaterals
Use quadrilateral properties that are unique to parallelograms to prove that the given shape is a parallelogram.
Illustrative Mathematics
Illustrative Mathematics: G Gpe a Midpoint Miracle
In this task, students are asked to draw a quadrilateral so that no two sides are congruent, no two angles are congruent, and no two sides are parallel. The task gives students the opportunity to prove that if we join the midpoints of a...
Texas Instruments
Texas Instruments: Perimeters, Areas, and Slopes Oh, My!
In this activity, students create geometric figures, and use analytic and coordinate geometry to investigate their attributes. They go through the process of proving that a quadrilateral is a parallelogram.
Maths Challenge
Maths challenge.net: Platonic Solids
A "three star geometry problem" requiring knowledge of how to complete geometric proofs to prove that there are no more than five regular convex polyhedra.