1.3 Adding and Subtracting Within 20

Unit Goals

  • Students add and subtract within 20. Students apply the properties of operations and the relationship between addition and subtraction.

Section A Goals

  • Build toward fluency with adding and subtracting within 10.

Section B Goals

  • Add and subtract one-digit numbers from teen numbers without composing or decomposing a ten.
  • Find the value that makes an addition or subtraction equation true, involving 10.
  • Understand 10 ones as a ten and the numbers 11 to 19 as a ten and some ones.

Section C Goals

  • Add within 20, including three addends.

Section D Goals

  • Subtract within 20.
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Glossary Entries

  • category
    A label that tells how objects in a group are alike.

  • data
    Information about the things or people in a group.

    Example: If you have a box of colored pencils, then the lengths and colors of each of the pencils are data about the pencils in the box.

  • difference
    The result when one number is subtracted from another.

  • sum
    The total when two or more numbers are added.

  • survey
    A way to collect data using a group of people answering the same question.

  • teen number

    A number with 1 ten and between 1 and 9 ones.

    Fifteen is 1 ten and 5 ones.