This Problem Set is a part of the Lesson 5, Unit 5, Grade 1. In this lesson, students begin by identifying the hidden shapes within a large square as they cut the seven tangram pieces from this special rectangle. Then they use the pieces to form new shapes from composite shapes, including recomposing the original square, and explore the variety of ways they can compose new shapes by positioning pieces alongside composite shapes. For example, students can not only form a larger triangle from two right triangles, but they can also use the shapes to form two composite triangles and push them together to make the original tangram square.