Fraction Classroom

Grade 5 / Fraction multiplication

Scaling Stories

Predict how a multiplier below, equal to or above one changes a quantity.

45 min · Grade 5 · Paper and pencils

Teaching companion · Version 2.0.0

Diagnose, reteach, and choose the next step

Compare the product with a positive starting quantity by comparing its factor with one.

The original lesson PDFs remain version 1.0.0. This supplement adds diagnostic probes, teaching responses, and question-specific rubrics. Use the supplement below for the updated guidance.

Begin with two short probes

Ask for an explanation or drawing before choosing a response. A wrong answer alone does not identify its cause.

  1. Before computing, predict whether 3/4 × 1/2 is below or above 3/4.

    Answer and teaching response for d1

    Look for: Below 3/4, because it takes half of that positive amount; the product is 3/8.

    If you observe: Predicts a larger result because the operation is multiplication.

    Respond: Fold a 3/4-length segment in half and compare the folded share with the full starting segment.

  2. Predict how multiplying 7/8 by 1 and by 4/3 changes the starting amount.

    Answer and teaching response for d2

    Look for: A factor of 1 preserves 7/8; a factor of 4/3 makes it larger.

    If you observe: Uses the numerator or denominator separately rather than comparing the whole factor with one.

    Respond: Represent 4/3 as one full copy plus another third-copy of the starting 7/8.

Compare the factor with one copy

  1. Fix a positive starting strip and make half a copy, one copy, and two copies.
  2. Record whether each result is smaller, equal, or larger before calculating.
  3. Test a factor such as 4/3 by decomposing it into one copy plus a fraction of another.

Check independently: Without computing the exact product, compare 5/6 × 2/5 with 5/6.

Answer to the reteaching check

The product is smaller because the positive factor 2/5 is below one.

Use the scaling short intervention if the difficulty persists. Return to this check before repeating the exit ticket.

Read both exit responses

  • e1 gives 3/8 for 3/4 × 1/2.
  • e2 states the positive-factor cases below one, equal to one, and above one.

Ready to continue

e1 meets its criterion: e1 gives 3/8 for 3/4 × 1/2. e2 also meets its criterion: e2 states the positive-factor cases below one, equal to one, and above one.

Continue to the linked next lesson. Use size predictions when a fractional amount is divided into equal smaller shares.

Next lesson: Unit Fraction Sharing

Revisit the calculation or model

e1 does not yet meet this criterion: e1 gives 3/8 for 3/4 × 1/2.

Ask the learner to explain the attempt, then use the matching diagnostic probe to identify the difficulty. Work through the focused reteach below and its check. Use the linked short intervention if the difficulty persists; retry e1 and e2 before moving on.

Open the linked short intervention

Strengthen the explanation

e1 meets its criterion, but e2 does not yet show this evidence: e2 states the positive-factor cases below one, equal to one, and above one.

Use three sketches with the same starting strip and factors 1/2, 1, and 2. Ask the learner to state all three e2 cases and connect the first to e1.

Open the linked short intervention
Question-by-question misconception guide and open-response criteria

Use these as follow-up prompts, then examine the learner’s model or explanation. Open responses may differ from the sample while satisfying the criteria.

c1: Calculate 3/4 × 1/2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c2: Calculate 3/4 × 1. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c3: Calculate 3/4 × 2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c4: Calculate 2/3 × 3/4. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c5: Calculate 2/3 × 3/2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c6: Calculate 5/6 × 2/5. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c7: Calculate 4/5 × 5/4. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

c8: Calculate 7/8 × 4/3. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

s1: Calculate 1/2 × 1/2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

s2: Calculate 1/2 × 1. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

s3: Calculate 1/2 × 2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

s4: Calculate 3/4 × 1/2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

h1: Why is 3/4 × 1/2 smaller than 3/4?

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

Look for in the response:

  • Interpret the factor 1/2 as taking half of the positive amount 3/4.
  • Show or state that the result is 3/8.
  • Explain that half of a positive amount is smaller than the starting amount.

h2: Give a counterexample to multiplication always makes numbers bigger.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

Look for in the response:

  • Provide a valid multiplication example using a positive factor below one.
  • Compute the product correctly.
  • Compare the product with the starting positive amount and show that it is smaller.

h3: What happens when a positive quantity is scaled by one?

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

Look for in the response:

  • Specify a positive starting quantity.
  • State that multiplying it by one preserves its value.
  • Explain using one complete copy of that quantity.

h4: Predict without computing whether 7/8 × 4/3 exceeds 7/8.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

Look for in the response:

  • Identify the scale factor 4/3 as greater than one.
  • Predict the product exceeds the starting 7/8.
  • Justify the prediction from scaling rather than requiring the exact product.

e1: Calculate 3/4 × 1/2. Show a model or your reasoning.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

e2: State the scaling rule for positive amounts.

Watch for: Assumes multiplication always enlarges a positive amount.

Try: Keep a 3/4-meter ribbon as the starting amount. Compare half a copy, one copy, and two copies. Record 3/8, 3/4, and 3/2 meters, then relate each change to a factor below, equal to, or above one.

Look for in the response:

  • For a positive starting amount, state that a positive factor below one makes it smaller.
  • State that a factor of one preserves it.
  • State that a factor greater than one enlarges it; connect the half-factor case to e1.

Materials for your group

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Preview the complete lesson

Eight core questions and a two-question exit ticket. Print one set per student.

c1. Calculate 3/4 × 1/2. Show a model or your reasoning.

c2. Calculate 3/4 × 1. Show a model or your reasoning.

c3. Calculate 3/4 × 2. Show a model or your reasoning.

c4. Calculate 2/3 × 3/4. Show a model or your reasoning.

c5. Calculate 2/3 × 3/2. Show a model or your reasoning.

c6. Calculate 5/6 × 2/5. Show a model or your reasoning.

c7. Calculate 4/5 × 5/4. Show a model or your reasoning.

c8. Calculate 7/8 × 4/3. Show a model or your reasoning.

e1. Calculate 3/4 × 1/2. Show a model or your reasoning.

e2. State the scaling rule for positive amounts.

Teaching notes & lesson sources

Designed for Grade 5. Predict how a multiplier below, equal to or above one changes a quantity.

5.NF.B.5b curriculum reference

Version 1.0.0. Original, AI-assisted lesson content. Free local classroom use; public reuse terms have not yet been assigned.

These lessons have not yet been field-tested in classrooms. Use the exit ticket and student explanations to decide what to revisit.