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.


Quarter 3
Quarter 4
Add within 100. Relate the strategy to a written method and explain the reasoning used. Including:

a. Adding a two-digit number and a one-digit number, within 100.

b. Adding a two-digit number and a multiple of 10, using:
concrete models drawings strategies based on place value, properties of operations, and the relationship between addition and subtraction
Add within 100. Relate the strategy to a written method and explain the reasoning used. Including:

a. Adding a two-digit number and a one-digit number, within 100.

b. Adding a two-digit number and a multiple of 10, using:
concrete models drawings strategies based on place value properties of operations
the relationship between addition and subtraction

c. Understand that in adding two-digit numbers, it requires adding tens and tens, ones and ones; and sometimes it is necessary to compose a ten (without standard algorithm)

Enduring Understanding

Understanding place value leads to number sense and efficient strategies for computation.

Essential Questions

How does a digit's position affect its value?

Vocabulary (online dictionary, HCPSS Vocabulary Cards)

add, compose, place value

About the Math

Students should work with invented strategies, number concepts, and operation concepts prior to learning the traditional algorithm. Working with open number lines is a good way to develop these concepts.

Rich Tasks for Multiple Means of Engagement, Expression, and Representation (UDL)

Little Ten-Frame Addition and Subtraction (Van de Walle, K-3, p 149). Provide a set of little ten-frame cards to each pair of students. One student makes a two-digit number with multiple ten-frames and ones (ex- 54 can be made with five full ten-frames and four ones). The second student may either select a one digit number or multiple full ten frames to show a two-digit multiple of ten. When both have their numbers ready, they place it out so both can see. Then they try to be the first to tell the total. For subtraction, again one student makes a two digit number with multiple ten-frames and ones. The second child writes on paper a one digit number or a multiple of 10 to be subtracted from the model number. Students should be encouraged to share strategies to see how fast they can get at solving

Students should initially be exposed to the computational strategy of direct modeling (counting by ones and the use of base ten models), then invented or flexible strategies, and finally the traditional algorithm. This will enable them to move from the concrete, then to the semi concrete, and finally to the abstract. Students may use a variety of methods to add, for example:

Journal Prompts:

  • Using 0-9 digit cards, turn over two cards to make a two-digit number. Roll your die and add the number shown. Record and repeat.
  • Represent 17 with base 10 blocks. Add another set of 10 and record the new number. Continue adding one more set of 10 until you reach 97. What pattern do you notice?
Problems:
Anna scored 18 points in 3 games. What might her scores have been for each of the games?
Juan added three numbers to get 14. What could the three numbers be?
The sum of a two-digit number and a one digit number is 43? What might the numbers be?
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Strategies for Addition:
Addition Strategies
This file outlines different strategies for adding whole numbers.
Add On Tens, Then Add Ones
You can decompose one of the numbers
33 + 26
33 and 20 is 53.
Then 6 more is 59.
Move Some to Make Tens
To add 33 + 26,students may add 33 + 7 = 40
Then think 19 + 40 = 59.
Add Tens, Add Ones, Combine
Students may split the tens and ones apart.
33 + 26 can be thought of as 30 + 20 + 3 + 6
30 + 20 = 50
3 + 6 = 9
50 + 9 -= 59

Print Resources

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Brain Compatible Activities for Mathematics K-1
(36-39, 57-59)

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Mental Math in the Primary Grades
(66-76)

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Number Talks





Web Resources:

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Games and Centers
Lessons
Student Resources
Video Segments
Printables
What Number is...?
Adding 2 Digit and One Digit Numbers
Adding Sets of Ten
The Game of Tens and Ones

Addition Split

Lucky 6

Lesson Seeds
Using Place Value to Teach Addition and Subtraction
Add and Subtract
Online Tools
How Many Cows?
100 Splat Squares

Practice Sheet / Homework
Computation with Sticks and Dots
(Erin Reisberg, Centennial Lane)
Discovering Math: Adding 1
Adding Two-Digit Numbers
Breaking Into Tens and Ones









Children's Literature

Click on the books for additional activities.
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Fair Bear Share



Questions/Comments:

Contact John SanGiovanni at jsangiovanni@hcpss.org.


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Howard County Public Schools Office of Elementary Mathematics Curricular Projects has licensed this product under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.