Topic Eleven: Subtract Within 1,000 Using Models and Strategies

Pacing (Duration of Unit):

Desired Results

Transfer:

Standards for Mathematical Practices
1. Make sense of problems and persevere in solving them.
2. Reason abstractly and quantitatively.
3. Construct viable arguments and critique the reasoning of others.
4. Model with mathematics.
5. Use appropriate tools strategically.
6. Attend to precision.
7. Look for and make use of structure.
8. Look for and express regularity in repeated reasoning.
Established Goals:
2.NBT.7 Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding and subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.

2.NBT.9 Explain why addition and subtraction strategies work, using place value and the properties of operations.

Student I Can Statements:
  • I can use strategies to subtract numbers within 1000 and know when to regroup.
  • I can explain why adding and subtracting strategies work using what I know about place value.

Prerequisite Standards:
1.NBT.2 Understand that the two digits of a two-digit number represent amounts of tens and ones.

1.NBT.2.a 10 can be thought of as a bundle of ten ones-called a "ten."

1.NBT.2.c The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones).

2.NBT.1a 100 can be thought of as a bundle of ten tens-called a "hundred."

2.NBT.1b The numbers 100, 200, 300, 400, 500, 600, 700, 800, 900 refer to one, two, three, four, five, six, seven, eight, or nine hundreds (and 0 tens and 0 ones).

2.NBT.2 Count within 1000; skip-count by 5s, 10s, and 100s.
Big Ideas:

Number and the Number Line-The set of real numbers is infinite and ordered. Whole numbers, integers, and fractions are real numbers. Each real number can be associated with a unique point on the number line.

The Base-Ten Numeration System-The base-ten numeration system is a scheme for recording numbers using digits 0-9, groups of ten, and place value.

Equivalence-Any number, measure, numerical expression, algebraic expression, or equation can be represented in an infinite number of ways that have the same value.

Operation Meanings and Relationships-There are multiple interpretations of addition, subtraction, multiplication, and division of rational numbers, and each operation is related to other operations.

Basic Facts and Algorithms-There is more than one algorithm for each of the operations with rational numbers. Some strategies for basic facts and most algorithms for operations with rational numbers, both mental and paper and pencil, use equivalence to transform calculations into simpler ones.

Practice, Processes, and Proficiencies-Mathematics content and processes can be applied to solve problems.
Essential Questions:

*What are strategies for subtracting numbers to 1,000?
Students will know...
  • Place-value patterns and basic facts can be used to help you mentally subtract 10 or 100 to any given three-digit number.
  • Three-digit numbers can be broken apart using hundreds, tens, and ones and subtracted in different ways. You can represent how you break apart and subtract numbers with hops or jumps in an open number line. You can count back or add up to subtract.
  • Three-digit numbers can be broke apart using hundreds, tens, and ones, and subtracted in different ways. You can change the numbers to make it easier to subtract mentally, without changing the difference.
  • The standard algorithm for three-digit numbers breaks the calculation into simpler calculations using place value, starting with the ones, then the tens, and then the hundreds. Answers to the simpler calculations are used to find the final difference.
  • Good math thinkers look for things that repeat in a problem. They use what they learn from one problem to help them solve other problems.

Vocabulary:
None
Students will be skilled at...

  • Subtract 10 or 100 mentally using place value.
  • Subtract 3-digit numbers using an open number line.
  • Subtract 3-digit numbers using mental math strategies.
  • Subtract 3-digit numbers using models.
  • Apply different subtraction strategies and explain why they work.
  • Think about and check their work as they solve problems.

Assessment Evidence

Performance Assessment:
Other Evidence:

Formative Assessment Tasks:

Learning Plan

Learning Activities:

11-1 Subtract 10 and 100

11-2 Count Back to Subtract on an Open Number Line

11-3 Add up to Subtract on and Open Number Line

11-4 Subtract Using Mental Math

11-5 Use Models to Subtract

11-6 Explain Subtraction Strategies

11-7 Math Practices and Problem Solving: Make Sense and Persevere
Resources: