# Working With Equal Groups

## In this unit students •  understand and reason about odd and even numbers; •  work with equal groups and rectangular arrays, using addition to find the total number of objects; •  partition rectangles into rows and columns of squares and count to find the total number of squares; •  understand nickels as groups of 5 pennies and quarters as groups of 5 nickels, and solve word problems involving money.

In this unit students use skip counting and addition to find the total number of objects given equal-sized sets. They are introduced to the idea of odd and even numbers. They write equations that express the total as a sum of equal addends, for example, the equations 4 + 4 + 4 = 12 and 3 + 3 + 3 + 3 = 12 represent the total number of objects in an array with four rows and three columns. This is foundational for the work students will do with multiplication in third grade, where they synthesize this information and understand that this means the same as 3 x 4 = 12 and 4 x 3 = 12. Students also work to create their own arrays by partitioning rectangles into rows and columns of same-size squares, and then counting them to find the total.

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