Preserve the whole and endpoint while multiplying both fraction counts by the same factor.
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.
Ask for an explanation or drawing before choosing a response. A wrong answer alone does not identify its cause.
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: The strip shows 2/4. Enter the same amount as a fraction.
Strip model: 1 same-sized whole, each divided into 4 equal parts; 2 parts are shaded altogether.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c2: Compare 1/2 and 2/4. Choose <, =, or >. The wholes are the same size.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c3: Compare 2/3 and 4/6. Choose <, =, or >. The wholes are the same size.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c4: Rename 3/4 as an equivalent fraction with denominator 8.
Strip model: 1 same-sized whole, each divided into 8 equal parts; 6 parts are shaded altogether.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c5: Compare 3/6 and 1/2. Choose <, =, or >. The wholes are the same size.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c6: Compare 2/5 and 4/10. Choose <, =, or >. The wholes are the same size.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c7: Write the value shown by eight of twelve parts.
Strip model: 1 same-sized whole, each divided into 12 equal parts; 8 parts are shaded altogether.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
c8: Compare 3/4 and 9/12. Choose <, =, or >. The wholes are the same size.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
s1: What amount is shaded? Count two fourths.
Strip model: 1 same-sized whole, each divided into 4 equal parts; 2 parts are shaded altogether.
Watch for: Reverses the shaded count and the total equal-part count.
Try: Use two labels: “equal pieces in one whole” under the bar and “pieces selected” above it. Point to every piece while naming the denominator, then only the selected pieces while naming the numerator.
s2: Compare 1/2 and 2/4. Choose <, =, or >. Split each half into two equal parts.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
s3: What amount is shaded? Count three sixths.
Strip model: 1 same-sized whole, each divided into 6 equal parts; 3 parts are shaded altogether.
Watch for: Reverses the shaded count and the total equal-part count.
Try: Use two labels: “equal pieces in one whole” under the bar and “pieces selected” above it. Point to every piece while naming the denominator, then only the selected pieces while naming the numerator.
s4: Compare 1/3 and 2/6. Choose <, =, or >. Split each third into two equal parts.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
h1: Give three different names for 2/3 and explain the common endpoint.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
Look for in the response:
- Give three distinct fraction names equal to 2/3; 2/3 itself may be one of them.
- Show the same factor applied to numerator and denominator for each renaming.
- Explain the common endpoint using the same whole or unit line.
h2: A partner says 2/3 = 3/4 because both numbers increased by one. Give a counterexample.
Watch for: Adds the same number to numerator and denominator and claims the fraction stays equal.
Try: Put 2/3 and 3/4 on the same twelfths strip: 8/12 and 9/12 have different endpoints. Contrast this with 2/3 = 4/6, where both counts are multiplied by two.
Look for in the response:
- Reject 2/3 = 3/4.
- Provide evidence of different values, such as 8/12 versus 9/12.
- Explain that adding one to both counts does not preserve the fraction as multiplying both by the same factor does.
h3: How could you rename 3/4 using twelfths?
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
Look for in the response:
- Identify the factor from fourths to twelfths as three.
- Multiply the three selected fourths by three to obtain nine twelfths.
- State 3/4 = 9/12 and preserve the same whole or shaded endpoint.
h4: Can unequal-length strips prove equal physical amounts? Explain.
Watch for: Assumes equal fraction labels guarantee equal physical amounts even when the wholes differ.
Try: Compare half of a 12 cm strip with half of a 6 cm strip. Measure 6 cm and 3 cm. Keep the fraction label visible and ask what changed; then repeat the comparison using two equal-length strips.
Look for in the response:
- Distinguish equal fraction values from equal physical lengths.
- Identify that the strips use unequal wholes.
- Explain that matching relative shares on those strips alone cannot prove equal lengths.
e1: Compare 3/6 and 1/2. Choose <, =, or >. The wholes are the same size.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
e2: Explain why 1/2 and 2/4 are equivalent.
Watch for: Changes one part of a fraction without scaling numerator and denominator by the same factor.
Try: Shade 2/3 of a fixed strip and split each third into two equal parts. Count four shaded sixths out of six. Write ×2 on both arrows and check that the shaded endpoint did not move.
Look for in the response:
- Keep the whole fixed when moving from halves to fourths.
- Split each half into two equal fourths, giving 1/2 = 2/4.
- Explain that the shaded amount or endpoint stays unchanged.