What balances?
http://illuminations.nctm.org/LessonDetail.aspx?ID=L119
A lesson plan for grades K–2 Mathematics
This lesson encourages students to explore another meaning of subtraction, the balance. They use subtraction facts to generate related addition facts and explore at the concrete level the idea of subtraction as the inverse of addition. Through a series of activities, the teacher demonstrates the concept of subtraction in mathematics.
Students will:
- Model the balance meaning of subtraction.
- Record subtraction modeled on the balance.
NCTM Standards and Expectations covered in this lesson include:
- Counting with understanding and recognize “how many” in sets of objects.
- Understanding various meanings of addition and subtraction of whole numbers and the relationship between the two operations.
- Developing and using strategies for whole-number computations, with a focus on addition and subtraction.
- Developing fluency with basic number combinations for addition and subtraction.
North Carolina Curriculum Alignment
Mathematics (2004)
Grade 1
- Goal 1: Number and Operations - The learner will read, write, and model whole numbers through 99 and compute with whole numbers.
- Objective 1.03: Develop fluency with single-digit addition and corresponding differences using strategies such as modeling, composing and decomposing quantities, using doubles, and making tens.
- Objective 1.04: Create, model, and solve problems that use addition, subtraction, and fair shares (between two or three).
Grade 2
- Goal 1: Number and Operations - The learner will read, write, model, and compute with whole numbers through 999.
- Objective 1.03: Create, model, and solve problems that involve addition, subtraction, equal grouping, and division into halves, thirds, and fourths (record in fraction form).
- Objective 1.05: Create and solve problems using strategies such as modeling, composing and decomposing quantities, using doubles, and making tens and hundreds.
