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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 › Addition, subtraction, estimation

    Add and subtract within 1000, abstract

    Add and subtract within 1000 using the standard algorithms (carry and borrow). Do not rely on manipulatives or drawings. Conclude by giving your students this challenge.

    The MAA associates this problem with 7.SP.C.8.b, but this problem has nothing to do with probability, it's just straight logical deduction.

    Watch these Khan Academy videos:

    • Missing number for 3-digit addition within 1000
    • Worked example: Subtracting 3-digit numbers (regrouping)
    • Worked example: Subtracting 3-digit numbers (regrouping twice)
    • Worked example: Subtracting 3-digit numbers (regrouping from 0)
    • Subtracting 3-digit numbers (regrouping)
    • Adding 3-digit numbers
    • Using place value to add 3-digit numbers: part 1

    Do these Khan Academy exercises:

    • Find the missing number (add and subtract within 1000)
    • Subtract within 1000
    • Add within 1000
    • Select strategies for adding within 1000
    • Break apart 3-digit subtraction problems
    • Select strategies for subtracting within 1000
    • Estimate to subtract multi-digit whole numbers
    • Subtract on a number line

    Next, give your students this challenge:

    The Set of Numbers by NRICH

    Conclude by leading this investigation:

    Recamán’s Sequence
    by MathPickle

    3.NBT.A.2: Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

    Lessons and practice problems