Unit 7

Numbers and Operations in Base Ten Place Value

 

Grade 1

Math

Unit Length and Description:

 

4 weeks

This unit will continue to focus on solving different types of addition and subtraction word problems and equations to 20. The unit serves as an introduction to using place value to solve addition problems involving two-digit and one-digit numbers.

Standards:

 

CCSS for Mathematical Content

CCSS #

CCSS Text

Operations and Algebraic Thinking

1.OA.1

Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

1.OA.2

Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

1.OA.3

Apply properties of operations as strategies to add and subtract. Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)

1.OA.4

Understand subtraction as an unknown-addend problem. For example, subtract 10 8 by finding the number that makes 10 when added to 8.

1.OA.6

Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use mental strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 4 = 13 3 1 = 10 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

1.OA.8

Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 =  3, 6 + 6 = .

Numbers and Operations in Base Ten

1.NBT.3

Compare two two-digit numbers based on meanings of the tens and ones digits, recording the results of comparisons with the symbols >, =, and <.

1.NBT.4

Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, 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 and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.


Standards for Mathematical Practice (MP)

MP.1

Make sense and persevere in solving problems.

MP.2

Reason abstractly and quantitatively.

MP.7

Look for and make use of structure.

Instructional Outcomes

1.OA.1: Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

  • I can use a symbol (e.g. ?, x) to represent an unknown number in a problem.
  • I can determine the operation to solve word problems with unknowns.
  • I can solve word problems by adding 3 numbers in different ways.

 

1.OA.2: Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

  • I can add 3 numbers.
  • I can identify parts/addends in a word problem.
  • I can show how to solve word problems.

 

1.OA.3: Apply properties of operations as strategies to add and subtract. Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)

  • I can explain how properties of addition and subtraction work.
  • I can use strategies to solve addition and subtraction problems.

 

1.OA.4: Understand subtraction as an unknown-addend problem. For example, subtract 10 8 by finding the number that makes 10 when added to 8.

  • I can identify the unknown in a subtraction problem.
  • I can solve subtraction problems to find the missing addend.
  • I can explain the relationship of addition and subtraction.

 

1.OA.6: Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use mental strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 4 = 13 3 1 = 10 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

  • I can add within 20.
  • I can subtract within 20.
  • I can use strategies to add and subtract within 20.
  • I can add fluently within 10.
  • I can subtract fluently within 10.

 

1.OA.8: Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 =  3, 6 + 6 = .

  • I can recognize part-part-whole relationships of three numbers
  • I can determine the missing value in an addition equation.
  • I can determine the missing value in a subtraction problem.

 

1.NBT.3: Compare two two-digit numbers based on meanings of the tens and ones digits, recording the results of comparisons with the symbols >, =, and <.

        I can identify the value of each digit in a two-digit number.

        I can explain what each symbol means (>, <, =).

        I can compare two 2 digit numbers.

        I can use >, <, = symbols to compare two 2 digit numbers.

 

1.NBT.4: Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, 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 and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.

        I can show that in adding 2 digit numbers, you add ones to ones and tens to tens.

        I can recognize when to regroup to compose (make) a ten.

        I can add a 2 digit number and a 1 digit number within 100.

        I can add a 2 digit number and 1 digit number with regrouping within 100.

        I can add a 2 digit number and a multiple of 10 within 100.

        I can relate the strategy to an equation.

        I can explain why I used a chosen strategy to solve a written equation.

 

 

Enduring Understandings:

 

        Students will solve various types of addition and subtraction word problems and equations using strategies.

        Students will use place value to compare two numbers.

        Students will add two-digit and one-digit numbers with and without composing a group of ten.

       Students will develop strategies for adding and subtraction whole numbers.

 

Essential Questions:

 

        What happens when we join two quantities or take one from another?

        How can we find the total when we join two quantities?

        How can we find what is left when we take one quantity from another?

        How can we find the difference when we compare one quantity to another?

        How can we compare one quantity to another?

        How can we represent problem situations?

        How can we show that addition and subtraction are related?