2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
MATH DOMAIN
Grade 2
Math Cluster
Use place value
understanding
and properties
of operations to
add and
subtract.
2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
August 2013
3
Math Standard
Mathematic Practices
2.NBT.7 Add and
subtract within
1000, using a variety
of strategies.
Understand that
sometimes it is
necessary to
compose and
decompose tens or
hundreds.
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.
(not tested)
Add and
subtract twodigit without
composing and
decomposing
(tested)
(tested)
Base Ten: Subtract any two- and
three-digit numbers.
Clarify Standard




Mental strategies AND Standard algorithm should be learned.
Adding numbers together is composing new numbers.
Subtracting and taking numbers apart is decomposing numbers.
The terms “composing” and “decomposing” replace “regrouping” and “borrowing” in
the CCSS Mathematics.
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2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
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.
1.NBT.6 Subtract multiples of 10 in the range 10-90 using a variety of strategies; explain
reasoning used.
Learning Tasks:
 Mental strategies can be effective when dealing with equations (sideways problems).
 Understand that when adding or subtracting multiple-digit numbers, like units are
added or subtracted together (hundreds + hundreds, tens + tens)
 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)
 An “up-and-down” addition or subtraction computation problem is called an algorithm.
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2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
 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.
 Here is one way to teach the standard algorithm for addition.
 By the end of 2nd grade students can transition to putting the “1” at the top of the
appropriate column.
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2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
 This is one way to teach the standard algorithm for subtraction.
2.NBT.7 Add and subtract within 1000, using a variety of strategies. Understand that
sometimes it is necessary to compose and decompose tens or hundreds.
Vocabulary
Prior





Making tens
Counting on
Hundreds
Tens
Ones








Explicit
Compose
Decompose
Making tens
Counting on
Thousands
Hundreds
Tens
Ones
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2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
2.NBT.7 Sample Assessment Items earning a “3” in the reporting system
 59 + 25= __________
172 + 38=__________
 468
+225
 67 - 39= _______
234 - 93 = ________
 454
- 363
The planets are interesting. A year on Earth lasts about 365 days. A “year” is how long it takes a
planet to circle the sun exactly one time. The amount of time it takes a planet to orbit the Sun is
figured out in “Earth days“or “Earth years.” Each Earth day is 24 hours. Sometimes how long a
planet takes to orbit around the Sun is figured out in “Earth years.” Each Earth year is about 365
days.
Venus orbits the Sun in about 225 Earth days. Mars orbits the Sun in about 687 Earth days.
Mercury orbits the Sun in 88 days.
 How many days less is Mercury’s orbit than Earth’s orbit?
 How many days less is Mercury’s orbit than Venus’s?
Assessment Rubric
1
No evidence of a strategy.
2
Evidence that the student used a correct strategy but answered incorrectly. OR The
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2.NBT.7/NUMBERS AND OPERATIONS IN BASE TEN
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.7 Sample Assessment Items earning a “4” in the reporting system
The planets are interesting. A year on Earth lasts about 365 days. A “year” is how long it takes
a planet to circle the sun exactly one time. The amount of time it takes a planet to orbit the
Sun is figured out in “Earth days” or “Earth years.” Each Earth day is 24 hours. Sometimes
how long a planet takes to orbit around the Sun is figured out in “Earth years.” Each Earth
year is about 365 days.
Venus orbits the Sun in about 225 Earth days. Mars orbits the Sun in about 687 Earth days. It
takes about 12 Earth years for Jupiter to orbit the Sun. Saturn orbits the sun about 18 Earth
years more than Jupiter.
Our Earth orbits the Sun almost 165 times before Neptune orbits it once. We have not seen
an entire orbit of Neptune (not one orbit!) since the planet was discovered. Jupiter takes
about 165 Earth years to go around the sun. Mercury orbits the Sun in 88 Earth days. It’s the
shortest!!
 How many days does it take for Saturn to orbit the sun exactly one time?
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