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    • ▾2nd grade
      • ▾Add and subtract within 20
        • •Add to count rectangular arrays
        • •Mentally add and subtract within 20
      • ▸Place value
        • •Place value with hundreds
        • •Convert between various representations, numbers within 1000
        • •Counting and skip-counting within 1000
        • •Intro to even and odd
        • •Compare three-digit numbers
      • ▸Add and subtract within 100
        • •Mentally add and subtract within 100
        • •Add and subtract within 100, abstract
        • •One-step word problems, add and subtract within 100
        • •Two-step word problems, add and subtract within 100
      • ▸Add and subtract within 1,000
        • •Add and subtract within 1,000
        • •Add multiple two-digit numbers
        • •Mentally add or subtract powers of ten
      • ▸Money and time
        • •Money word problems, including dollars
        • •Tell and write time, five minute increments
      • ▸Measurement
        • •Compare lengths by measuring
        • •Estimate lengths
        • •Add and subtract within 100 to solve word problems involving lengths
        • •Add and subtract within 100 on the number line
      • ▸Data
        • •Plot measurements on a line plot
        • •Draw picture and bar graphs
      • ▸Geometry
        • •Partition rectangles into rows and columns
        • •Area of a rectangle by counting unit squares
        • •Partition circles and rectangles into equal shares
        • •Draw shapes with certain attributes
        • •Intro to tessellations
     › 2nd grade › Add and subtract within 20

    Add to count rectangular arrays

    Use addition to find the total number of objects arranged in rectangular arrays, with up to 5 rows and 5 columns. See that we could add in two different ways. That is, we could add along the rows or along the columns.

    Adding with arrays by Khan Academy

    Adding with arrays by Khan Academy

    Next, students will solve word problems, some involving arrays, and others involving just repeated addition. The aforementioned skills will prepare students for multiplication and the idea that multiplication is commutative. However, the word "multiplication" shouldn't be used at this time.

    Watch these Khan Academy videos:

    • Using arrays in word problems
    • Repeated addition: haircuts

    Array word problems by Khan Academy

    Conclude by exploring this game.

    Conclude by leading this investigation:

    Solidarity – Poland, 1981 (addition, logic)
    by MathPickle

    2.OA.C.4: Use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns; write an equation to express the total as a sum of equal addends.

    Additional lessons and practice problems