An array is an arrangement of a set of objects organized into equal groups in rows and columns. Arrays help make counting easy. Counting by equal groups is more efficient than counting objects one by one. The ten- frame is an array used in Kindergarten. Students count objects in arrays in Kindergarten and Pre- Kindergarten. (PK.CC.4) The rectangular array is used to teach multiplication and leads to understanding area. (3.OA.3)
Arrays reinforce the meaning of multiplication as repeated addition (e.g., 3 x 4 = 4 + 4 + 4), and the two meanings of division—that 12 ÷ 3 can indicate how many will be in each group if I make 3 equal groups and that it can also indicate how many groups I can make if I put 3 in each group. Further using arrays reinforces the relationship between multiplication and division.