During Unit 2, your children will compare whole numbers (at least to 100) to develop understanding of and solve problems involving their relative sizes.  They will think of whole numbers between 10 and 100 in terms of tens and ones (especially recognizing the numbers 11 to 19 as composed of a ten and some ones).  Through activities that build number sense, they will understand the order of the counting numbers and their relative magnitudes.

Printable Parent Letter

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Key Vocabulary: Add, Addends, Compare, Data, Difference, Equal, Euation, Fewer, Graph, Less, More, Number, Numeral, Ones, Place Value, Subtract, Strategy, Sum, Tens, Two Digit Number, Unknown

Your children need to:

  • 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.

    Counting to 120

    Counting Patterns
  • Understand that the two digits of a two-digit number represent amounts of tens and ones.  Understand the following as special cases:
    • 10 can be thought of as a bundle of ten ones – called a “ten”
    • The numbers from 11 to 19 are composed of a ten and one, two, three, four, five six, seven, eight, or nine ones.
    • The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two , three, four, five, six, seven, eight, and nine tens (and 0 ones)

Tens and Ones

Compose 2-Digit Numbers

Representing Numbers
  • Compare two two-digit numbers based on meanings of tens and ones digits, recording the results of comparisons with the symbols >, =, <.
    Comparing 2-Digit Numbers

    Comparing with Symbols
  • Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

    Tens on a Hundred Chart
    Ten More

    Ten Less
  • Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).

    Tens on a Hundred Chart
       Ten More
    Ten Less

    Solve for Missing Parts
  • 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.
    Solving Word Problems

    Solving Compare Problems
  • Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
    Solving 3 Addends

    3 Addends Associative Property
  • Organize, represent, and interpret data with up to three categories; ask and answer questions about the total number of data points, how many in each category, and how many more or less are in one category than in another.
Using a Bar Graph

Collect and Organize Data