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    • ▾3rd grade
      • ▸Addition, subtraction, estimation
        • •Mentally add within 1000
        • •Round to the nearest 10 or 100
        • •Add and subtract within 1000, abstract
      • ▸Multiplication
        • •Multiplication using rectangular arrays and equal groups, concrete and visual
        • •Multiplication as repeated addition
        • •Multiply, abstract
      • ▸Division
        • •Divide using equal groups
        • •Division as repeated subtraction
        • •Divide, abstract
      • ▸Fractions
        • •Equal shares of shapes and unit fractions
        • •Plot fractions on the number line
        • •Relating fractions to 1
        • •Representing whole numbers as fractions
        • •Comparing fractions with like numerators, denominators, or both
      • ▸Relating multiplication and division
        • •Missing number problems, multiplication and division
        • •Relating multiplication to division
        • •Use properties to multiply and divide
        • •Multiply one-digit numbers by multiples of 10
      • ▸Arithmetic patterns and problem solving
        • •Two-step word problems
        • •Arithmetic and geometric sequences
        • •Patterns in addition and multiplication
        • •Intro to the triangular numbers
        • •Intro to the Fibonacci sequence
        • •Intro to Pascal's triangle
      • ▾Geometry
        • •Shape heirarchy
        • •Area of composite rectangles by counting unit squares
        • •Area and units of measure
        • •Area as multiplication
        • •Area, perimeter, and how they're related
      • ▸Time, measurement, and data
        • •Tell and write time, minute increments
        • •Measure and estimate volumes and masses
        • •Scaled bar and picture graphs
        • •Line plots with fractions
     › 3rd grade › Geometry

    Area of composite rectangles by counting unit squares

    Find area of composite rectangles (rectilinear figures) by counting unit squares. There are two ways students can find area by counting unit squares. The first, is to give students a figure with the squares drawn. Then students just have to count to find the area. The second, is to give students square tiles, which they can use to tile the figure, then count the number of tiles to determine the area.

    Intro to area and unit squares by Khan Academy

    Compare area with unit squares by Khan Academy

    TODO: This exercise is about comparing areas. Find one for determining areas as well.

    Conclude by giving your students this challenge, then this one. The first puzzles is quite easy, the second quite difficult! Students should make sure the figures will have the same area before moving pieces around.

    Conclude by leading this investigation:

    Armenian Rug Puzzles (logic)
    by MathPickle

    3.MD.C.6: Measure areas by counting unit squares (square cm, square m, square in, square ft, and improvised units).

    Additional lessons and practice problems