Use addition to find the total number of objects arranged in rectangular arrays, with up to 5 rows and 5 columns. See that we could add in two different ways. That is, we could add along the rows or along the columns.

Adding with arrays by Khan Academy

Adding with arrays by Khan Academy

Next, students will solve word problems, some involving arrays, and others involving just repeated addition. The aforementioned skills will prepare students for multiplication and the idea that multiplication is commutative. However, the word "multiplication" shouldn't be used at this time.

Watch these Khan Academy videos:

Array word problems by Khan Academy

Conclude by exploring this game.

Conclude by leading this investigation:

Solidarity – Poland, 1981 (addition, logic)

by MathPickle

2.OA.C.4: Use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns; write an equation to express the total as a sum of equal addends.