The learner visualizes how two or more familiar two-dimensional shapes, such as triangles, squares, rectangles, or circles, can fit together to form a larger shape and can identify the resulting whole and its component parts without relying on physical rearrangement. This reasoning includes recognizing that a shape’s identity is unchanged by turning or flipping it and supports later understanding of geometric structure, partitioning, area, and perimeter.
When you compose shapes, picture smaller shapes fitting together to make one larger shape. A shape is still the same shape when you turn it or flip it.
Example: Two matching triangle pieces are each shaped like half of a square. What larger shape can they make?
So, the whole shape is a square, and its parts are two triangles.
You can check your thinking by asking: “Do the pieces fit with no gaps or overlaps?” If they do, you have composed the larger shape mentally.
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