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• Math: Developing 2-Digit Addition and Subtraction Strategies

# Math: Developing 2-Digit Addition and Subtraction Strategies

### Suggested Time Frame: 19 Instructional Days

##### Focus TEKS

Adding and Subtracting with 2-Digit Numbers

• Computation
• 2.4B add up to four two-digit numbers and subtract two-digit numbers using mental strategies and algorithms based on knowledge of place value and properties of operation
• Problem Solving
• 2.4C solve one-step and multi-step word problems involving addition and subtraction within 1,000 [120 in this unit] using a variety of strategies based on place value, including algorithms
• 2.4D generate and solve problem situations for a given mathematical number sentence involving addition and subtraction of whole numbers within 1,000 [120 in this unit].
• Representing
• 2.7C represent and solve addition and subtraction word problems where unknowns may be any one of the terms in the problem
##### Numeracy TEKS

Counting Patterns (Suggested: 4 days)

• 2.5A determine the value of a collection of coins up to one dollar [pennies, nickels, and dimes only in this unit]
• 2.5B use the cent symbol, dollar sign, and the decimal point to name the value of a collection of coins
• RRISD 2.7B Skip count forward and backward by ten and one hundred from any given number up to 1,000

Building Fluency with Addition and Subtraction within 20 (Suggested: 11 days)

• 2.4A recall basic facts to add and subtract within 20 with automaticity [Including the Use-Doubles Strategy for Addition; Including the Think Addition Strategy for Subtraction]
##### Spiral Review TEKS

1st Grade Measuring Length and Telling Time  (Suggested: 15 days)

• 1.7D  Describe a length to the nearest whole unit using a number and a unit
• 1.7A  Use [non-standard] measuring tools to measure the length of objects to reinforce the continuous nature of linear measurement
• 1.7B  Illustrate that the length of an object is the number of same-size units of length that, when laid end-to-end with no gaps or overlaps, reach from one end of the object to the other
• 1.7C  Measure the same object/distance with units of two different lengths and describe how and why the measurements differ
• 1.7E  Tell time to the hour and half hour using analog and digital clocks

Counting Quantities (Suggested: 4 days, using both numeracy and spiral review time)

• RRISD 2.1 organize and count a collection of objects and create a recording of how the objects were counted
• 2.1C  select tools, including real objects, manipulatives, paper and pencil, and technology as appropriate, and techniques, including mental math, estimation, and number sense as appropriate, to solve problems;
• 2.1E  create and use representations to organize, record, and communicate mathematical ideas;