Standard #: MAFS.2.NBT.2.9 (Archived Standard)


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


General Information

Subject Area: Mathematics
Grade: 2
Domain-Subdomain: Number and Operations in Base Ten
Cluster: Use place value understanding and properties of operations to add and subtract. (Major Cluster) -

Clusters should not be sorted from Major to Supporting and then taught in that order. To do so would strip the coherence of the mathematical ideas and miss the opportunity to enhance the major work of the grade with the supporting clusters.

Date Adopted or Revised: 02/14
Date of Last Rating: 02/14
Status: State Board Approved - Archived

Related Courses

Course Number1111 Course Title222
5012040: Mathematics - Grade Two (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 and beyond (current))
7712030: Access Mathematics Grade 2 (Specifically in versions: 2014 - 2015, 2015 - 2018, 2018 - 2022, 2022 and beyond (current))
5012005: Foundational Skills in Mathematics K-2 (Specifically in versions: 2019 - 2022, 2022 and beyond (current))


Related Resources

Formative Assessments

Name Description
Explaining the Standard Algorithm for Subtraction

Students are asked to explain each step of a subtraction problem completed by using the standard algorithm.

Explaining the Standard Algorithm for Addition

Students are asked to explain each step of an addition problem completed by using the standard algorithm.

Using Place Value

Students are asked to solve a two-digit addition problem using a place value strategy and then are asked to explain why this strategy works.

Counting Up To Subtract

Student are asked to consider why a counting strategy works to solve subtraction problems.

Lesson Plans

Name Description
Subtracting 9 the

In this lesson, students will use the hundreds chart to discover a strategy to subtract 9 from different numbers. Students will learn and practice the compensation strategy of subtracting 10 and then adding 1 back to get the final difference. Students will also learn and practice visualizing to “mentally see” the hundreds chart and use it as an efficient mental math strategy to subtract 9 from any given two-digit number.

Adding 9 the

In this lesson, students will use the hundreds chart to discover a strategy to add 9 to different numbers. Students will then learn to visualize the hundreds chart as an efficient mental math strategy to add 9 to any given two-digit number.

Tutorials

Name Description
Subtracting with regrouping

In this tutorial video from Khan Academy, a subtraction problem is solved which contains two numbers each with two-digits. The video demonstrates subtraction with regrouping using the standard algorithm, as well as a method using expanded form.

Subtracting two-digit numbers without regrouping

In this video tutorial from Khan Academy, explore subtracting two-digit numbers by using the standard algorithm. This video does not include regrouping.

Subtraction by Regrouping This 8-minute video demonstrates how to perform subtraction with regrouping. The presenter uses base-10 blocks to explain the rationale and to make a visual connection with the standard algorithm. The examples involve 2-digit and 3-digit numbers.

Student Resources

Tutorials

Name Description
Subtracting with regrouping:

In this tutorial video from Khan Academy, a subtraction problem is solved which contains two numbers each with two-digits. The video demonstrates subtraction with regrouping using the standard algorithm, as well as a method using expanded form.

Subtracting two-digit numbers without regrouping:

In this video tutorial from Khan Academy, explore subtracting two-digit numbers by using the standard algorithm. This video does not include regrouping.



Parent Resources

Tutorials

Name Description
Subtracting with regrouping:

In this tutorial video from Khan Academy, a subtraction problem is solved which contains two numbers each with two-digits. The video demonstrates subtraction with regrouping using the standard algorithm, as well as a method using expanded form.

Subtracting two-digit numbers without regrouping:

In this video tutorial from Khan Academy, explore subtracting two-digit numbers by using the standard algorithm. This video does not include regrouping.



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