Students will develop strategies to estimate object length in standard units, measure differences in length, and use addition and subtraction to find the difference between two objects’ lengths. This unit extends second graders’ prior study of standard length units, and using addition and subtraction within 100. Students may struggle with basic measurement skills, mentally picturing length benchmarks in order to estimate, as well as the risktaking inherent in estimation.
Key Concepts:
 We can use our knowledge of units to estimate lengths.
 Measurement can be used to determine how much longer one object is than another.
 Addition and subtraction can be used to compare measured or estimated lengths of objects.
Prior Knowledge Needed:
 Objects can be measured using tools such as rulers; (Grade 2, Unit 2; 2.MD.A.1, 2.MD.A.2, 2.MD.A.5)
 Adding and subtracting numbers within 100; (Grade 2, Unit 1; 2.NBT.B.3 2.OA.B.2)
 Directly comparing two objects with a measurable attribute in common; (Grade K, Unit 8; K.MD.A.2)
Units on the Horizon:
 Developing strategies for addition and subtraction (Grade 3, Unit 3)
 Solving problems involving shapes (Grade 3, Unit 13)
Lessons

Lesson objective: Understand that length can be estimated by using mental images of units (inches in this lesson), comparing to objects of known length, and comparing to benchmark objects. Students bring prior knowledge of estimating length from explori...

Lesson objective: Understand that length in inches can be estimated by comparing to benchmark objects  finger joints and dollar bills. Students bring prior knowledge of estimating length from exploring standard units of measure in Grade 2. This prior k...

Lesson objective: Understand that length (in centimeters) can be estimated by comparing to benchmark objects  an index finger width. Students bring prior knowledge of estimating length from exploring standard units of measure in Grade 2. This prior kno...

Lesson objective: Apply estimating length concepts to solve a problem. This lesson provides an opportunity for students to apply their knowledge and understanding of estimating lengths to a reallife situation. Students are asked to estimate the lengths...

Lesson objective: Understand that measurement can be used to determine how much longer one object is than another. Students bring prior knowledge of measuring to determine length differences from exploring standard units of measure in Grade 2. This prio...

Lesson objective: Measure the difference in length between two objects. This lesson helps to build fluency with measuring length difference. A centimeter ruler is used here because it supports directly measuring differences. This work develops students'...

Lesson objective: Apply measuring differences in length between two objects. This lesson provides an opportunity for students to apply their knowledge and understanding of measuring differences to a reallife situation. Students are asked to find multip...

Lesson objective: Understand that addition and subtraction can be used to compare measured or estimated lengths of objects. Students bring prior knowledge of determining length differences through addition and subtraction from 2.MD.4 (Differences in len...

Lesson objective: Add and subtract to compare measured or estimated lengths of objects. This lesson helps to build procedural skills with finding length differences through addition and subtraction. An inch ruler is used here because it supports the con...

Lesson objective: Solve problems using addition and subtraction to compare measured or estimated lengths of objects. This lesson provides an opportunity for students to apply their knowledge and understanding of finding length differences through adding...