Standard - 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.

Standard - NY-2.NBT.6:
Add up to four two-digit numbers using strategies based on place value and properties of operations.

Standard - 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.

Standard - 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.

Standard - NY-2.NBT.8:
Mentally add 10 or 100 to a given number 100-900, and mentally subtract 10 or 100 from a given number 100-900.

Standard - NY-2.NBT.9:
Explain why addition and subtraction strategies work, using place value and the properties of operations.