# 2.Nbt.5/Numbers and Operations in Base Ten

2.NBT.5/NUMBERS AND OPERATIONS IN BASE TEN

MATH DOMAIN /**2.NBT.5/NUMBERS AND OPERATIONS IN BASE TEN**

Grade 2

Math Cluster / Math Standard /

**Mathematic Practices**

**Use place value understanding and properties of operations to add and subtract.**/ 2.NBT.5 Fluently add and subtract within 100 using a variety of strategies. / 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.

**Reporting Standards**/ Trimester 1 / Trimester 2 / Trimester 3

**Base Ten: Add any two- and three-digit numbers.**

**Base Ten: Subtract any two- and three-digit numbers.**/ Introduced (not tested)

Add and subtract with no composing or decomposing / (tested) / (tested)

**Clarify Standard**

v

**Mental strategies AND Standard algorithm should be learned.**

v Adding numbers together is composing new numbers.

v Subtracting and taking numbers apart is decomposing numbers.

v The terms “

**composing” and “decomposing**” replace “regrouping” and “borrowing” in the CCSS Mathematics.

Task Analysis

1.NBT.4 Add within 100 using a variety of strategies., 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 and ones and ones; and sometimes it is necessary to compose a ten.

Learning Tasks:

v Mental strategies can be effective when dealing with equations (sideways problems).

v Understand that when adding or subtracting multiple-digit numbers, like units are added or subtracted together (hundreds + hundreds, tens + tens)

v Use addition and subtraction mental strategies within 100:

· Counting on

· Making a ten ( 29 + 5 change to 30 + 4)

· Decomposing a number leading to a ten

o 54 + 26 =

o 54 + 20 = 74

o 74 + 6 = 80

· Related equations ( 5 + 7 = 12 is related to 1 2- 7 = 5)

· Doubles

· Doubles +/- 1 (80 + 81 is 80 +80 = 160 plus 1 more is 161)

v An “up-and-down” addition or subtraction computation problem is called an algorithm.

v In order to ensure consistency across the elementary schools in Auburn SD, second graders need to learn what is called “the standard algorithms” for two- and three-digit addition and subtraction.

v Here is one way to teach the standard algorithm for addition.

v By the end of 2nd grade students can transition to putting the “1” at the top of the appropriate column.

v This is one way to teach the standard algorithm for subtraction.

2.NBT.5 Fluently add and subtract within 100 using a variety of strategies.

Vocabulary

Prior / Explicit

· Making tens

· Counting on

· Hundreds

· Tens

· Ones / · Compose

· Decompose

· Making tens

· Counting on

· Hundreds

· Tens

· Ones

**2.NBT.5 Sample Assessment Items**earning a “3” in the reporting system

Name of Bird / Longest Lifespan Recorded

Allen’s Hummingbird / 4 years

Bald Eagle / 22 years

Brown Pelican / ?

Canada Goose / 24 years

Chickadee / 12 years

Crow / 15 years

Ruby-Throated Hummingbird / 9 years

Look at the data chart of the life spans of different kinds of birds. Usually the larger the bird, the longer it lives. The longer life spans are found in the bigger birds.

v According to the data chart, how much longer does a Bald Eagle live than a Crow? Show your equation.

A Brown Pelican lives 5 times longer than an Allen’s Hummingbird according to this data chart.

v How long does a Brown Pelican live? Show your equation.

Assessment Rubric

1 / No evidence of a strategy.

2 / Evidence that the student used a correct strategy but answered incorrectly. OR The student answered correctly with no evidence of strategy.

3 / Evidence that the student used a correct strategy, and correct equation, and answered correctly.

4 /

**On a level 4 question:**Evidence that the student used a correct strategy, and correct equation, and answered correctly.

**1.NBT.5 Sample Assessment Items**earning a “4” in the reporting system

Name of Bird / Longest Lifespan Recorded

Allen’s Hummingbird / 4 years

Bald Eagle / 22 years

Blue Jay / ?

Broad-Tailed Hummingbird / ?

Canada Goose / 24 years

Chickadee / 12 years

Crow / 15 years

Ruby-Throated Hummingbird / 9 years

Look at the data chart of the life spans of different kinds of birds. Usually the larger the bird, the longer it lives. The longer life spans are found in the bigger birds.

According to the data chart, a Broad-Tailed Hummingbird lives half the life span of a Bald Eagle. A Blue Jay lives 5 years longer than a Broad-Tailed Hummingbird.

v How long does a Blue Jay live according to the data chart?

When 4 different types of bird’s life spans are added together, the total is 41 years.

v What 4 kinds of birds were used to get the sum of 41 years? Write an equation.

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