In this unit, students will continue to work on adding and subtracting multidigit numbers and will be introduced to adding and subtracting in the hundreds place. Students will apply previously learned strategies of adding and subtracting within 100 to adding and subtracting within 1,000. This unit relies heavily on a solid foundational understanding of place value with threedigit numbers and the properties of addition and subtraction.
Key Concepts:
 We use place value to add threedigit numbers.
 Sometimes, we compose or decompose tens or hundreds when adding or subtracting threedigit numbers.
 The sum of two numbers is invariant, regardless of the strategy we use to add them.
 A group of addends always has the same sum no matter what strategy we use to add them.
Prior Knowledge Needed:
 Developing addition and subtraction strategies; (Grade 1, Unit 6; 1.OA.B.4)
 Understanding ten ones make a ten; (Grade 1, Unit 1; 1.NBT.B.2a)
 Use place value to read, write, represent, and compare numbers; (Grade 1, Unit 8; 1.NBT.B.2c)
Units on the Horizon:
 Demonstrating fluency in addition and subtraction (Grade 2, Unit 15)
 Developing strategies for addition and subtraction (Grade 3, Unit 3)
Lessons

Lesson objective: Understand that addition and subtraction strategies used with twodigit numbers can be applied to threedigit numbers. Students bring prior knowledge of adding and subtracting using place value from 2.NBT.B.5. This prior knowledge is e...

Lesson objective: Add and subtract threedigit numbers without regrouping. This lesson helps to build fluency with whole number threedigit addition and subtraction without regrouping. Base ten blocks and number lines are used here because they support ...

Lesson objective: Add and subtract threedigit numbers without regrouping. This lesson provides an opportunity for students to apply their knowledge and understanding of threedigit addition and subtraction without regrouping to a mathematical situation...

Lesson objective: Extend understanding of adding and subtracting threedigit numbers to include regrouping. Students bring prior knowledge of adding and subtracting threedigit numbers from 2.NBT.B.9. This prior knowledge is extended to problems that re...

Lesson objective: Add two threedigit numbers where it is necessary to regroup 10 ones to make a new ten, or 10 tens to make a new hundred. This lesson helps to build fluency with whole number threedigit addition with regrouping. Base ten blocks and nu...

Lesson objective: Add two threedigit numbers involving regrouping 10 ones to make a new ten, and/or 10 tens to make a new hundred. This lesson provides an opportunity for students to apply their knowledge and understanding of threedigit addition with ...

Lesson objective: Subtract two threedigit numbers involving regrouping 1 ten to make 10 ones, or 1 hundred to make 10 tens. Students bring prior knowledge of adding and subtracting threedigit numbers from 2.NBT.B.9. This prior knowledge is extended to...

Lesson objective: Understand and solve threedigit subtraction problems, with regrouping, as missing addend problems. Students bring prior knowledge of adding and subtracting threedigit numbers from 2.NBT.B.9. This prior knowledge is extended to solvin...

Lesson objective: Subtract two threedigit numbers involving regrouping using place value strategies and the relationship between addition and subtraction. This lesson helps to build fluency with whole number threedigit subtraction with regrouping. Tap...

Lesson objective: Add and subtract two threedigit numbers involving regrouping using place value strategies and the relationship between addition and subtraction. This lesson provides an opportunity for students to apply their knowledge and understandi...

Lesson objective: Understand that a group of addends always has the same sum regardless of what strategy is used to add them. Students bring prior knowledge that when adding twodigit numbers, we add tens with tens and ones with ones from 1.NBT.C.4. Thi...

Lesson objective: Add more than two addends that involve composing a new ten or hundred. This lesson helps to build procedural skill with finding the sum of three and four twodigit addends. Composing a ten or hundred is used here because it enhances th...

Lesson objective: Apply strategies to find the sum of addition problems with three and four twodigit addends. This lesson provides an opportunity for students to apply their knowledge and understanding of known addition strategies to a mathematical sit...

Lesson objective: Add four twodigit addends. This lesson helps to build procedural skill with adding four twodigit addends. Students select the addition strategies used here because they are applying known strategies to solve problems as they see appr...

Lesson objective: Apply strategies to solve addition problems with four twodigit addends. This lesson provides an opportunity for students to apply their knowledge and understanding of addition with many addends to a reallife situation. Students are a...