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.
2.NBT.6 Add up to four two-digit numbers using strategies based on place value and properties of
operations.
2.NBT.7 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 method. Understand that in adding or
subtracting 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.
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.
2.NBT.9 Explain why addition and subtraction strategies work, using place value and the properties of
operations. (Explanations may be supported by drawings or objects.)
1.OA.1 Use addition and subtraction within 20 to solve word problems involving situations of adding
to, taking from, putting together, taking apart, and comparing, with unknowns in all
positions, e.g., by using objects, drawings, and equations with a symbol for the unknown
number to represent the problem.
1.OA.3 Apply properties of operations as strategies to add and subtract. (Students need not use
formal terms for these properties.) 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.4 Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by
finding the number that makes 10 when added to 8.
1.NBT.2 Understand that the two digits of a two-digit number represent amounts of tens and ones.
Understand the following as special cases:
a. 10 can be thought of as a bundle of ten ones – called a “ten.”
b. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six,
seven, eight, or nine ones.
c. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six,
seven, eight, or nine tens (and 0 ones).