6th Grade Accelerated Math Lesson
Parallelograms: Area by Decomposition and Composition
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Advanced 6th Grade BTC Style / Thinking Classrooms6.G.3.aDetermine the area of quadrilaterals and triangles by composition and decomposition of these shapes, as well as applications of properties and formulas. Quadrilaterals include parallelograms and trapezoids.40 min
Learning Objective
Students will determine the area of parallelograms by composing and decomposing shapes, connecting the base-height formula to the rectangle area formula.
Lesson Overview
Students discover the area formula for parallelograms by decomposing and rearranging them into rectangles, then apply the formula with increasing complexity through 12 thin-sliced tasks at vertical surfaces.
Materials
- Vertical whiteboards or large chart paper
- Dry-erase markers (multiple colors)
- Pencils and paper for notes
Scaffolded Task Progression
1Task 1
A rectangle has a base of cm and a height of cm. Draw it and find its area.
[ Interactive graph / diagram, available in the full lesson ]
[ Interactive graph / diagram, available in the full lesson ]
2Task 2
Here is a parallelogram on dot paper. The base is cm and the height is cm (the perpendicular distance). Draw a vertical cut on the left triangle and slide it to the right to make a rectangle. What is the area?
[ Interactive graph / diagram, available in the full lesson ]
[ Interactive graph / diagram, available in the full lesson ]
3Task 3
A parallelogram has a base of cm and a height of cm (the height is already marked with a dashed perpendicular line). Without cutting, write the area formula and calculate the area.
[ Interactive graph / diagram, available in the full lesson ]
[ Interactive graph / diagram, available in the full lesson ]
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