• TOC
  • Courses
  • Blog
  • Twitch
  • Shop
  • Search
    • Courses
    • Blog
    • Subreddit
    • Discord
    • Log in
    • Sign up
    • ▾1st grade
      • ▸Place value
        • •Count and write numbers within 120
        • •Skip count by 3s and 4s
        • •Place value with tens
        • •Compare two-digit numbers
      • ▾Addition and subtraction
        • •River crossing puzzles
        • •Add and subtract within 20
        • •Add within 20, word problems involving three addends
        • •Use one addition problem to solve another
        • •Add by making tens
        • •Subtract by adding
        • •Understand the equals sign
        • •Add and subtract within 20, missing number problems
        • •Add and subtract within 20, word problems
        • •Add within 100, concrete and pictorial
        • •10 more or 10 less
        • •Subtract multiples of ten from multiples of ten
      • ▸Measurement, data, and geometry
        • •Order without tools
        • •Measure given a unit
        • •Bar and picture graphs having three categories of data
        • •Tell and write time, hour and half-hours
        • •Definitions of shapes
        • •Compose 2D and 3D shapes
        • •Halves and quarters
     › 1st grade › Addition and subtraction

    Subtract by adding

    Solve subtraction problems by thinking about what needs to be added to the subtrahend to reach the minuend. For example, 10 - 8 = __ can be solved by thinking about what needs to be added to 8 to reach 10.

    Relating addition and subtraction by Khan Academy

    Relate addition and subtraction by Khan Academy

    Conclude by leading this investigation:

    Cookie Monster Problem
    by MathPickle

    1.OA.B.4: Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.

    Additional lessons and practice problems