Lesson objective: Extend understanding of area for rectangles and parallelograms to circles.

Students bring prior knowledge of the area of two dimensionsal shapes from grade 4 (4.MDA.3). This prior knowledge is extended to circles as students decompose a circle to determine the formula for the area of a circle. A conceptual challenge students may encounter is how to break up the circle into similar shapes that can be reassembled into a parallelogram.

The concept is developed through work with a circle drawing that students experiment with in order to find the area formula.

This work helps students deepen their understanding of equivalence because the area of the two shapes (a circle and a parallelogram) are equivalent (and so the area of the circle can be calculated).

Students engage in Mathematical Practice #1 (Make sense of problems and persevere in solving them) as they experiment with decomposing the circle into different shapes, discovering which is the best to reassemble into the parallelogram.

**Key vocabulary:**

- area
- circle
- diameter
- radius

**Special materials needed:**