Standard #: MA.2.AR.2.2


This document was generated on CPALMS - www.cpalms.org



Determine the unknown whole number in an addition or subtraction equation, relating three or four whole numbers, with the unknown in any position.


Examples


Determine the unknown in the equation begin mathsize 12px style 45 plus square equals 23 plus 46 end style.

Clarifications


Clarification 1: Instruction extends the development of algebraic thinking skills where the symbolic representation of the unknown uses any symbol other than a letter. 

Clarification 2: Problems include having the unknown on either side of the equal sign.

Clarification 3: Addition and subtraction are limited to sums up to 100 and related differences. Refer to Situations Involving Operations with Numbers (Appendix A).



General Information

Subject Area: Mathematics (B.E.S.T.)
Grade: 2
Strand: Algebraic Reasoning
Status: State Board Approved

Benchmark Instructional Guide

Connecting Benchmarks/Horizontal Alignment

 

Terms from the K-12 Glossary

  • Equation 
  • Equal Sign 
  • Expression

 

Vertical Alignment

Previous Benchmarks

 

Next Benchmarks

 

 

Purpose and Instructional Strategies

The purpose of this benchmark is to build relational thinking. In grade 1, students determined an unknown whole number in an addition or subtraction problem within 20.
  • Instruction includes an unknown value in any position. 
  • Instruction includes compensation of values to balance equations. 
  • Instruction includes the use of number lines, drawings, or models to solve addition and subtraction problems.

 

Common Misconceptions or Errors

  • Students may confuse the value on one side of the equation with an unknown number. 
  • Students may think equivalent values have to look identical. 
  • Students may incorrectly use compensation to add or subtract.

 

Strategies to Support Tiered Instruction

  • Teacher provides opportunities to draw quantities in an equation and use drawings to determine the unknown. Teacher provides an organizer to help students represent the quantities. 
    • For example, 5 + 7 = ___ + 9. 
a number organizer
  • Teacher provides opportunities to create a drawing to represent an equation by decomposing numbers on each side. The focus should be on the quantities being equal even though they look different. 
    • For example, 20 + 7 = 10 + 17. 
A drawing to represent an equation by decomposing numbers on each side
  • Teacher provides opportunities to use a number balance to support understanding of finding an unknown quantity in a balanced equation. 
    • For example, students build the equation 4 + 5 = ____ + 7 on a number balance. Students then determine the value of the unknown quantity by balancing the number balance. This builds understanding that the two sides of the equation must be equal. If students try to use 9 as the unknown quantity, it will not balance. 
number balance
  • Teacher provides number strings to teach compensation strategies based on number relationships. The teacher may reveal one line at a time and give students time to think about their responses. As students move through the string, the teacher asks questions to help draw attention to the target strategy of compensation. Students illustrate their thinking using manipulatives such as base 10 blocks or illustrations. 
    • Example:
base 10 blocks

 

Instructional Tasks

Instructional Task 1 (MTR.5.1)

A student solved for the missing addend in 30 + 43 = 26 +__ . The student says the missing addend is 47 because 26 is 4 less than 30, so we can add 4 more to 43 and that is 47. Using this strategy determine the missing addend in the equation below and justify your thinking.  


16 + 37 = __+ 38 

Instructional Task 2 (MTR.4.1

Provide students the opportunity to use other strategies to determine the unknown in the equation 16 + 37 = __+ 38. Allow students to discuss which method they prefer.

 

Instructional Items

Instructional Item 1 

Write a number in the blank that makes the equation true. 54 − __ = 32 − 15 

 

*The strategies, tasks and items included in the B1G-M are examples and should not be considered comprehensive.




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 Access Points

Access Point Number Access Point Title
MA.2.AR.2.AP.2 Determine the unknown whole number in an addition or subtraction equation, relating three whole numbers, with the change or result unknown (e.g., 7 + __ = 10, 10 − 3= __). Sums may not exceed 20 and their related subtraction facts.


Related Resources

Formative Assessments

Name Description
What Number Makes the Equation True?

Students find the missing number in an equation relating four whole numbers.

Relating Four Whole Numbers

Students find the missing number in an equation relating four whole numbers that involves addition and subtraction.

Determine the Missing Addend

Students find the missing addend in an addition equation relating five whole numbers.

Lesson Plans

Name Description
Are Your Numbers Equal to My Numbers?

This is a lesson that reinforces the meaning of the equal sign while students determine the unknown whole number in an addition equation.

Is it "Most Magically Magical"?

This lesson is intended to be a cooperative inquiry-based activity used close to the end of second grade. The students will be actively engaged in adding and subtracting numbers within 100 while having fun completing Magic Squares.

Original Student Tutorial

Name Description
Balancing Act

Help Tyler balance equations by finding the unknown number in this interactive tutorial.

Perspectives Video: Teaching Idea

Name Description
Equations on the Math Balance

Unlock an effective teaching strategy for teaching inequalities and equations with the math balance in this Teacher Perspectives video for educators.

Student Resources

Original Student Tutorial

Name Description
Balancing Act:

Help Tyler balance equations by finding the unknown number in this interactive tutorial.



Printed On:3/28/2024 3:18:43 PM
Print Page | Close this window