Lesson objective: Understand that we can count to answer how many objects are arranged in a line or a rectangular array.

Students bring prior knowledge of rote counting from K.C.1. This prior knowledge is extended to arranging objects in a straight line or array as students learn to count efficiently. A conceptual challenge students may encounter is transitioning from rote counting to one-to-one correspondence.

The concept is developed through work with counters, which represent objects and numbers.

This work helps students deepen their understanding of operations because as students practice counting objects in a line, row, or set, this builds toward an understanding of putting numbers together.

Students engage in Mathematical Practice 1 (Make Sense of Problems and Persevere in Solving them). Students slide shapes into five frames in order to count the number of shapes.

**Key vocabulary:**

- arrange
- count
- straight
- ten frame

**Special materials needed:**

- counters
- ten frame