3.NBT.3

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  • April 14, 2014 at 3:17 pm #3023
    Anonymous
    Inactive

    In some cases of introducing operations on a limited scale, for example in 4.NF.4b, the order of numbers matters – 3 x (1/2) is OK, but (1/2) x 3 is a 5th grade expectation. Are students expected to perform, say, 4 x 80 only or 80 x 4 too in third grade?

    3.NBT.3. Multiply one-digit whole numbers by multiples of 10 in the range 10–90 (e.g., 9 × 80, 5 × 60) using strategies based on place value and properties of operations.

    April 18, 2014 at 10:03 pm #3029
    lhwalker
    Participant

    I think you are correct that the standard is focused on the structure where a single digit is multiplied by a multiple of ten. As a high school teacher I use the K-8 standards to remediate, and many of my students are surprised when I point out (as they are reaching for a calculator) that 2 x 80 is simply doubling eight tens. Worse, most of them think they need to put a one under the 2 to multiply 2 x 1/8. So it makes sense to have a time of focus on the particular structure where a single digit comes first. However, that doesn’t negate 3.OA.B.5 where students apply the commutative property.

    May 2, 2014 at 5:09 pm #3049
    Bill McCallum
    Keymaster

    Lane basically has it right here: 3.NBT.3 is about 4 x 80, and 3.OA.5 allows for students reasoning from this to 80 x 4. But the emphasis in Grade 3 would be on 4 x 80.

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