In this unit, students will build upon their understandings of measurement of length as the concept of number lines is introduced. Students apply the structure of a ruler to visualizing and drawing number lines with equal spaces between consecutive numbers. They then use the number line as a tool to solve one and twostep addition and subtraction problems. It will be critical in this unit for students to understand that we count the spaces between numbers on a number line, not the numbers themselves.
Key Concepts:
 We can represent whole numbers as lengths from 0 on a number line diagram with equally spaced points corresponding to the numbers 0, 1, 2, ...,
 We can use a number line to solve many types of addition and subtraction problems related to length.
 We can use a number line to solve many types of addition and subtraction problems.
Prior Knowledge Needed:
 Compare two twodigit numbers; (Grade 1, Unit 13; 1.NBT.B.3)
 Measure length in standard units; (Grade 2, Unit 1; 2.MD.2)
 Add and subtract whole numbers within 20; (Grade 1, Unit 9; 1.OA.C)
Units on the Horizon:
 Generating and representing measurement data to solve problems; (Grade 2, Unit 9)
 Estimating and comparing lengths; (Grade 2, Unit 14)
 Demonstrating fluency in addition and subtraction; (Grade 2, Unit 15)
Lessons

Lesson objective: Understand that whole numbers can be represented as lengths from 0 on a number line diagram with equally spaced points corresponding to the numbers 0, 1, 2, etc. Students bring prior knowledge of the structure of rulers or other tools ...

Lesson objective: Students will practice representing numbers as lengths on a number line. This lesson helps to build procedural skill with representing lengths on a number line. A number line diagram is used here because it provides a continuous repres...

Lesson objective: Students will understand that number lines can be used to model addition and subtraction problems related to length. Students bring prior knowledge of the structure of a number line diagram from 2.MD.B.6. This prior knowledge is extend...

Lesson objective: Students will add two or more lengths using a number line. This lesson helps to build procedural skill with whole number addition. A number line diagram is used here because it highlights partwhole relationships and supports the strat...

Lesson objective: Find the difference between lengths using a number line. This lesson helps to build procedural skill with whole number subtraction. A number line diagram is used here because it highlights partwhole relationships and supports the stra...

Lesson objective: Solve problems by using a number line to add and subtract lengths. This lesson provides an opportunity for students to apply their knowledge and understanding of addition and subtraction to a reallife situation. Students are asked to ...

Lesson objective: Understand that number line diagrams can be used to model addition and subtraction of whole numbers that are not lengths. Students bring prior knowledge of adding and subtracting lengths using a number line from 2.MD.B.5. This prior kn...

Lesson objective: Use number line diagrams to solve addition and subtraction problems which describe "adding to" or "taking from" situations with a missing result, start, or change. This lesson helps to build fluency with whole number addition and subtr...

Lesson objective: Use number line diagrams to solve addition and subtraction problems, which describe "adding to" or "taking from" situations with a missing result, start, or change. This lesson helps to build fluency with whole number addition and subt...

Lesson objective: Solve 2step story problems that involve addition and/or subtraction using a number line. This lesson provides an opportunity for students to apply their knowledge and understanding of modeling addition and subtraction problems on a nu...