New York State Learning Standards and Core Curriculum
NY-2.OA. Operations & Algebraic Thinking
Add and Subtract within 20.
NY-2.OA.2a. Fluently add and subtract within 20 using mental strategies. Strategies could include: making ten; decomposing a number leading to a ten; using the relationship between addition and subtraction; creating equivalent but easier or known sums; and counting on.
NY-2.OA.2b. Know from memory all sums within 20 of two one-digit numbers.
NY-2.NBT. Number & Operations in Base Ten
Use place value understanding and properties of operations to add and subtract.
NY-2.NBT.5. Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
NY-2.NBT.7a. Add and subtract within 1000, 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 representation.
NY-2.NBT.7b. Understand that in adding or subtracting up to three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones, and sometimes it is necessary to compose or decompose tens or hundreds.
NY-2.NBT.9. Explain why addition and subtraction strategies work, using place value and the properties of operations.