Unit 5

Addition and Subtraction within 1000 with Word Problems to 100

 

Grade 2

Math

Unit Length and Description:

 

15 days

 

In Unit 5 students extend their understanding of a unit to build the foundation for multiplication and division wherein any number, not just powers of ten, can be a unit. Making equal groups of “four apples each” establishes the unit “four apples” (or just four) that can then be counted: 1 four, 2 fours, 3 fours, etc. Relating the new unit to the one used to create it lays the foundation for multiplication: 3 groups of 4 apples equal 12 apples (or 3 fours is 12).

 

Standards:

 

Major Cluster: NBT – Numbers and Operations in Base Ten

Understand Place Value

2.NBT.2

Count within 1,000; skip-count by 5s, 102, and 100s.

Supporting Cluster: OA – Operations and Algebraic Thinking

Work with equal groups of objects to gain foundations for multiplication.

2.OA.3

Determine whether a group of objects (up to 20) has an odd or even number of members, e.g., by pairing objects or counting them by 2s; write an equation to express an even number as a sum of two equal addends.

2.OA.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.

Additional Cluster: G - Geometry

Reason with shapes and their attributes.

2.G.2

Partition a rectangle into rows and columns of same-size squares and count to find the total number of them.

 

Standards for Mathematical Practice: Should be evident in every lesson.

3. Construct viable arguments and critique the reasoning of others.

4. Model with mathematics.

7. Look for and make use of structure.

8. Look for and express regularity in repeated reasoning.

Instructional Outcomes

2.NBT.2: Count within 1,000; skip-count by 5s, 102, and 100s.

  • I can count within 1000 from any given number.
  • I can skip-count by 5s from any given number.
  • I can skip-count by 10s from any given number.

 

2.OA.3: Determine whether a group of objects (up to 20) has an odd or even number of members, e.g., by pairing objects or counting them by 2s; write an equation to express an even number as a sum of two equal addends.

  • I can count a group of objects up to 20 by 2s.
  • I can recognize groups that have even numbers of objects will pair evenly up to 20.
  • I can recognize groups that have odd numbers of objects will not pair evenly up to 20.
  • I can determine whether a group of objects is odd or even using a strategy.
  • I can prove that all even numbers can be formed from the addition of two equal addends.
  • I can write and equation to express a given even number as a sum of two equal addends.

 

2.OA.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.

  • I can identify a rectangular array with up to 5 rows and up to 5 columns.
  • I can understand that arrays can be written as repeated addition problems.
  • I can write and solve repeated addition problems to find the number of objects using rectangular arrays.

 

2. G.2: Partition a rectangle into rows and columns of same-size squares and count to find the total number of them.

  • I can count to find the total number of same size squares.
  • I can define partition.
  • I can determine how to partition a rectangle into same size squares.
  • I can partition a rectangle into same size squares.

 

Enduring Understandings:

 

• There are similarities between skip counting and repeated addition.

• Repeatedly adding the same quantity, using a grouping picture, or forming a rectangular array are strategies for representing repeated addition equations.

·   Arrays one way of representing both repeated addition and skip counting.

• Explore and be able to explain even and odd numbers while using manipulatives.

• An even number can be decomposed into two equal addends.

• Double addition facts assist in recognizing even numbers.

 

Essential Questions:

 

• How do I determine if a number is odd or even?

• How are arrays and repeated addition related?

• How can rectangular arrays help us with repeated addition?

• How can we model repeated addition on the number line?

• How can we a model repeated addition equation with an array?

• How does skip counting help us solve repeated addition problems?