SECOND GRADE > 2.NBT.5 > TEACHER GUIDE

## TEACHER GUIDE TO CLARIFICATION

###### 2.NBT.5

Use place value understanding and properties of operations to add and subtract.

2.NBT.5 Fluently add and subtract within 100 using strategies based on place valueproperties of operations, and/or the relationship between addition and subtraction.

###### Defining Place Value Strategies

There are multiple ways students can use and apply their knowledge of Place Value. This

standard calls for students to use strategies. Students can use strategies, manipulatives

and pictorial representations. (Below are 4 strategies named in standard 1.OA.6

Example 28 + 67

Student 1

20 + 60 = 80

8 + 7  = 15

80 + 15 = 95

Student 3

Making 10

28 + 67

28 + 2 + 65

28 + 2=30

30 + 65 = 95

Decompose the 67

into 2 and 65 so I

can have 2 ones to

make 28 a 30.

Student 2

Counting on by 10

28 + 10 + 10 + 10 + 10 + 10 + 10

88 + 7  = 95

Student 4

Create easier or known sums

In grade two the use of a visual like baseten blocks would be beneficial to show how you can move the ones around

30 + 60 = 90

plus 5 more ones = 95

28 + 67

Move 2

When teaching these Place Value strategies the approach the teacher takes is just as important. A recommendation is to let students solve the problem in any way that works for them, then elaborate on how they solved the problem. Given the problem 32 + 25 students can solve the problem a few different ways. It is up to the teacher to recognize how they solved it and then identify that strategy to the other students. This promotes student - discovery learning. The teacher then truly becomes a facilitator of learning.

In this grade level, the conceptual understanding is being developed. In grade 4, students will learn the

standard algorithm with regrouping

Addition based on Place Value 32 + 25

Place Value- I can break the numbers into tens and ones.

I can breaks the numbers into tens 30 + 20 which = 50

I can break the numbers into ones 2 + 5 which = 7

Count on

Place Value- I can count on

32 + 20 = 52

Then count on the ones

52 + 5 = 57

Making Ten

Place Value- I can make a ten

I will start with 32 and add the 5 ones which leaves me with 20. Now I have 37 and I still need 3 to get to the next ten 40, so I borrowed 3 from 20 and I am left with 17. 40 + 17 = 57

Subtraction Based on Place Value 61 – 27

Open Number Line

Place Value with an open number line (this is interesting to see how the students “hop” up

the number line) This will build number sense and eventually, students will not need the

number line visually and they can solve this subtraction problem mentally.

the target number 61

Add up by tens and ones (mental version of open number line)

Place Value

27 + 30 = 57

57 + 4 = 61

Subtract by tens and ones (mental version of open number line)

Place Value

61 - 27

61 – 10 = 51, 51 – 10 = 41, 41 – 7 = 34

###### Coherence and Connections: Need to Know

3.NBT.2

1.NBT.4

1.NBT.5

1.NBT.6

2.NBT.5

2.OA.1

2.OA.

This is fluency Standard

Fluency Expectations or Examples of Culminating Standards

2.NBT.B.5 Fluently add and subtract within 100 using strategies based on place

value, properties of operations, and/or the relationship between addition and

subtraction.

Students can also show their fluency using an efficient, general algorithm.18

18 For the difference between a computation strategy and a computation algorithm, see the glossary of

the standards (page 85, under the letter “c” for “computation”).

PARCC Draft Model Content Frameworks: Mathematics Grades K-2

So, let’s go to the Standards Document glossary pg. 85

Computation algorithm. A set of predefined steps applicable to a class of problems that gives the correct result in every case when the steps are carried out correctly. See also: computation strategy.

Computation strategy. Purposeful manipulations that may be chosen for specific problems, may not have a fixed order, and may be aimed at converting one problem into another. See also: computation algorithm.

Understanding place value (cluster 2.NBT.A) is the foundation for using place value

understanding and the properties of operations to add and subtract (cluster 2.NBT.B).

(Mastery of the two clusters can grow over time in tandem with one

another.) Adding and subtracting within 1,000 (2.NBT.B.7) involves adding or subtracting hundreds with hundreds, tens with tens and ones with ones, sometimes composing or decomposing tens or hundreds. These ideas and methods rest on an understanding of the place value units (2.NBT.A.1, building on 1.NBT.A.2).

PARCC Draft Model Content Frameworks: Mathematics Grades K-2

Use place value understanding and properties of operations to add and subtract

Students become fluent in two-digit addition and subtraction.2.NBT.5, 2.NBT.6.

Representations such as manipulative materials and drawings may be used to support reasoning and explanations about addition and subtraction with three-digit numbers. 2.NBT.7

When students add ones to ones, tens to tens, and hundreds to hundreds they are

implicitly using a general method based on place value and the associative and

Common Core Standards Writing Team. (2013, September 19).

Progressions for the Common Core State Standards in Mathematics(draft). K-5 Number and Operations in Base 10Tucson, AZ: Institute for Mathematics and Educations, University of Arizona.

For this standard students are only required to add and subtract within 100.

Also check out Student Achievement Partners Coherence Map.

FYI:

2.NBT.5 is from

the 2.NBT.B

cluster

###### Classroom Resources

2.NBT.5 Daily Discourse

###### HOT Questions
1. How many tens are in the sum of the addition problem 16 + 39

2. How many ones are in the difference of the subtraction problem 23 – 18

3. Solve the addition problem two different ways 67 + 24

4. Why would I split up the numbers this way in order to add?

27 + 14

20   +  7  +  10  +  3  +  1 =

5. Explain how you can move the base-ten blocks in order to solve the addition problem