### TEKS

1.1 Mathematical process standards. The student uses mathematical processes to acquire and demonstrate mathematical understanding. The student is expected to:

• B. Use a problem-solving model that incorporates analyzing given information, formulating a plan or strategy, determining a solution, justifying the solution, and evaluating the problem-solving process and the reasonableness of the solution.
• C. 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.
• D. Communicate mathematical ideas, reasoning, and their implications using multiple representations, including symbols, diagrams, graphs, and language as appropriate.
• E. Create and use representations to organize, record, and communicate mathematical ideas.
• F. Analyze mathematical relationships to connect and communicate mathematical ideas.
• G. Display, explain, and justify mathematical ideas and arguments using precise mathematical language in written or oral communication.

1.3 Number and operations. The student applies mathematical process standards to develop and use strategies for whole number addition and subtraction computations in order to solve problems. The student is expected to:

• A. Use concrete and pictorial models to determine the sum of a multiple of 10 and a one-digit number in problems up to 99
• B. Use objects and pictorial models to solve word problems involving joining, separating, and comparing sets within 20 and unknowns as any one of the terms in the problem such as 2 + 4 = [ ]; 3 + [ ] = 7; and 5 = [ ] – 3.
• C. Compose 10 with two or more addends with and without concrete objects.
• D. Apply basic fact strategies to add and subtract within 20, including making 10 and decomposing a number leading to a 10.
• E. Explain strategies used to solve addition and subtraction problems up to 20 using spoken words, objects, pictorial models, and number sentences.
• F. Generate and solve problem situations when given a number sentence involving addition or subtraction of numbers within 20.

1.5 Algebraic reasoning. The student applies mathematical process standards to identify and apply number patterns within properties of numbers and operations in order to describe relationships. The student is expected to:

• E. Understand that the equal sign represents a relationship where expressions on each side of the equal sign represent the same value(s).
• F. Determine the unknown whole number in an addition or subtraction equation when the unknown may be any one of the three or four terms in the equation.
• G. Apply properties of operations to add and subtract two or three numbers.

### Common Core

Operations & Algebraic Thinking:
Understand and apply properties of operations and the relationship between addition and subtraction.

• 1.OA.B.3 Apply properties of operations as strategies to add and subtract.2 Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)
• 1.OA.B.4 Understand subtraction as an unknown ­addend problem. For example, subtract 10 ­ 8 by finding the number that makes 10 when added to 8.