In the first section of this unit, students determined whether a group of objects was odd or even by organizing them into pairs or putting them into 2 equal groups.

In this lesson, students describe the structure of an array. They describe the number of objects in each row of an array and learn that the total number of objects in an array can be determined by finding the sum of the number of objects in each row. Although students may describe many features of the arrays in the lesson, the focus is on describing the rows of the array. They attend to the number of rows, the number in each row, and the total number of objects. In the next lesson, students will be encouraged to describe the columns of an array and will use this term in future lessons.

In previous lessons, students explained why a number of objects was even or odd using diagrams and by skip-counting by 2. In this lesson, how did students use the structure of arrays to make sense of skip-counting and finding total amounts without counting by 1?