In this unit, students arrange objects in rectangular arrays. They will use the arrays for skip counting, repeated addition, and equal partitioning, in order to build foundations for multiplication in third grade. This unit will extend studentsâ€™ prior knowledge of counting within 1000 and skip counting by 5s, 10s and 100s. Students may struggle to organize a set of objects into equal groups, particularly when having to partition a rectangle into samesized squares.
Key Concepts:
 A group of objects can be organized in an array and thought of as a number of equal groups.
 Skipcounting or repeated addition can be used to find the total number of objects in an array because there is the same number of objects in every row or column.
 A rectangle can be partitioned into rows and columns of samesized squares.
Prior Knowledge Needed:
 Work with addition and subtraction; (Grade 1, Unit 13; 1.OA.7)
 Add and subtract within 20; (Grade 1, Unit 2; 1.OA.C)
 When representing arrays with rows of 2 or 5, students may add to find the total and naturally point out a connection to skipcounting by twos or fives; (Grade 2 Unit 8; 2.NBT.2)
 Defining attributes of rectangles (1.G.1 and 1.G.2)
 Add up to four twodigit numbers using strategies based on place value and properties of operations (2.NBT.6)
 A rectangle can be partitioned into halves, thirds, and fourths.
Units on the Horizon:
 Exploring equal groups as a foundation for multiplication and division (Grade 3, Unit 1. 3.OA.1, 3.OA.2)
 Developing conceptual understanding of area; (Grade 3, Unit 2, 3.OA.5, 3.MD.7)
Lessons

Lesson objective: Understand that a group of objects can be organized in an array. Students bring prior knowledge of equal groups using odd and even numbers from 2.OA.3. This prior knowledge is extended to arrays as students organize groups of objects i...

Lesson objective: Design arrays. This lesson helps to build the procedural skill of designing arrays for a given number of objects. Designing arrays is used here because it requires students to design arrays with an equal number of objects in each row a...

Lesson objective: Apply knowledge of organizing objects into equal groups to create arrays. This lesson provides an opportunity for students to apply their knowledge and understanding of arrays to a reallife situation. Students are asked to help a char...

Lesson objective: Understand that skip counting and repeated addition strategies can be used to find the total number of a set of objects in an array. Students bring prior knowledge of skip counting by twos or fives from 2.NBT.2 and their work with addi...

Lesson objective: Create arrays to represent a given number. This lesson helps to build fluency with creating arrays. Drawing arrays is used here because it requires students to create arrays with an equal number of objects in each row and column. This ...

Lesson objective: Write repeated addition equations to represent arrays. This lesson helps to build procedural skills with writing repeated addition equations. Providing a number to create an array is used here because it supports writing the repeated a...

Lesson objective: Apply their knowledge about arrays to find the total number of objects in a set. This lesson provides an opportunity for students to apply their knowledge and understanding of arrays to a reallife situation. Students are asked to help...

Lesson objective: Understand that a rectangle can be partitioned into equal rows and columns to create an array. Students bring prior knowledge of defining attributes of rectangles from 1.G.1 and 1.G.2. This prior knowledge is extended to partitioning a...

Lesson objective: Apply the skip counting strategy by rows to find the total number of objects in an array. This lesson provides an opportunity for students to apply their knowledge and understanding of skip counting to a reallife situation. Students a...

Lesson objective: Solve problems using skip counting and repeated addition. This lesson provides an opportunity for students to apply their knowledge and understanding of arrays to a reallife situation. Students are asked to help a friend solve a probl...
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