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Multiplication as scaling

CONCEPTUAL
MathematicsFractions|Ages 10—11|ID: mt_VKW8lOcFaw

Interpret multiplication as scaling (resizing): compare the size of a product to a factor based on the size of the other factor without computing; explain the effect of multiplying by fractions greater than, equal to, or less than 1

Mastery Evidence

  • Predict without calculating whether 3/4 × 7 is greater or less than 7
  • Explain why multiplying by 5/3 makes a number larger and multiplying by 2/5 makes it smaller
  • Relate multiplying a/b by n/n = 1 to the principle of fraction equivalence

Assessment Prompt

“If [child] multiplies 20 by 1/4, can they predict whether the answer will be bigger or smaller than 20 — and explain why, before doing the calculation?”

Prerequisites3

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