OAS 6.GM.2.1 (Oklahoma, 6th Grade): "Develop and use formulas for the area of squares and parallelograms using a variety of methods including but not limited to the standard algorithms and finding unknown measures." The worksheets below practice this standard. Each one is a free printable PDF with an answer key, comes in multiple versions, and can also be assigned digitally - no login or account needed.
Geometry & Measurement (GM)6.GM.2 Use mathematical modeling to calculate the area of squares, parallelograms, and triangles to solve problems.6.GM.2.1Develop and use formulas for the area of squares and parallelograms using a variety of methods including but not limited to the standard algorithms and finding unknown measures.