• 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

    River crossing puzzles

    Students will be given possible and impossible variants of Alcuin's river crossing puzzle. Go to this page. Give all puzzles except those found on the slides Hungry Monsters and Hungry Monsters Pt. 2. Two additional variants of the classic puzzle, both of which are impossible, can be found here and here.

    Conclude by leading this investigation:

    Tribute to Eric Carl
    by MathPickle