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Topic: Number and Operations in Base Ten 

Common Core Mathematics K-2

 Cluster  Work with numbers 11–19 to gain foundations for place value.
  Kindergarten
   K.NBT.1.Compose and decompose numbers from 11 to 19 into ten ones and some further ones, e.g., by using objects or drawings, and record each composition or decomposition by a drawing or equation (e.g., 18 = 10 + 8); understand that these numbers are composed of ten ones and one, two, three, four, five, six, seven, eight, or nine ones.
 Cluster  Extend the counting sequence.
  Grade 1
   1.NST.1.Count to 120, starting at any number less than 120. In this range, read and write numerals and represent a number of objects with a written numeral.
 Cluster  Understand place value.
  Grade 1
   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).
   1.NBT.3.Compare two two-digit numbers based on meanings of the tens and ones digits, recording the results of comparisons with the symbols >, =, and <.
 Cluster  Use place value understanding and properties of operations to add and subtract.
  Grade 1
   1.NBT.4.Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, 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 and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
   1.NBT.5.Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
   1.NBT.6.Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), 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 and explain the reasoning used.
 Cluster  Understand place value.
  Grade 2
   2.NBT.1.Understand that the three digits of a three-digit number represent amounts of hundreds, tens, and ones; e.g., 706 equals 7 hundreds, 0 tens, and 6 ones. Understand the following as special cases:
a. 100 can be thought of as a bundle of ten tens −called a "hundred."
b. The numbers 100, 200, 300, 400, 500, 600, 700, 800, 900 refer to one, two, three, four, five, six, seven, eight, or nine hundreds (and 0 tens and 0 ones).
   2.NBT.2.Count within 1000; skip-count by 5s, 10s, and 100s.
   2.NBT.3.Read and write numbers to 1000 using base-ten numerals, number names, and expanded form.
   2.NBT.4.Compare two three-digit numbers based on meanings of the hundreds, tens, and ones digits, using >, =, and < symbols to record the results of comparisons.
 Cluster  Use place value understanding and properties of operations to add and subtract.
  Grade 2
   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 threedigit 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.]