Repartition shaded strips to explain why equivalent fractions multiply both counts by the same factor.
Listen for the idea
Equivalent fractions count the same amount using different-sized equal parts.
Connect a common factor to splitting every original part equally.
Reject rules that change only one count or add the same number to both counts.
Materials: Paper strips; Pencil and ruler.
A 12-minute route
2 minutes: Try the three diagnostic questions. Ask for a brief explanation.
3 minutes: Teach one worked example that addresses the difficulty.
5 minutes: Choose three practice tasks and discuss the reasoning.
2 minutes: Give one transfer task independently and decide the next step.
The second worked example, three unused practice tasks, and remaining transfer task are available for a follow-up session. Allow more time if the group needs to build the models.
Teaching move: Shade first, then draw new partition lines without changing the shaded boundary. Count what happened to both the shaded pieces and all pieces in the whole.
Use the answer notes to interpret what you hear. Choose a response for each question to get a suggested teaching step. These choices describe this brief check and are not a mastery score.
1 A strip shows 2/3 shaded. Every third is split into two equal pieces. What fraction is now shaded?
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 4/6. The amount stays fixed while both counts double.
Listen for this difficulty: Doubling the denominator but leaving the numerator unchanged.
Try this response: Split both shaded thirds as well as the unshaded third, then recount.
Look for:
Names 4/6.
Explains that the shaded amount did not change.
2 Which equals 2/5: 3/6 or 4/10? Explain the transformation.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 4/10. Both numerator and denominator are multiplied by 2.
Listen for this difficulty: Adding the same number to both terms preserves value.
Try this response: Compare the shaded boundaries of two same-sized strips.
Look for:
Selects 4/10.
Links the factor of 2 to splitting every fifth in half.
3 Complete 3/4 = __/12. What happened to each fourth?
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 9/12. Each fourth was split into three equal pieces.
Listen for this difficulty: Adding 8 to both terms because 4 + 8 = 12.
Try this response: Draw three small pieces inside each fourth and count the shaded ones.
Look for:
Supplies numerator 9.
Explains the factor of 3.
2 · Model together
Two worked examples
Use one now. Ask the learner to explain each step before revealing the next part of your drawing.
1 Show why 2/3 = 8/12 with one strip.
Divide one strip into three equal parts and shade two.
Split every third into four equal pieces.
Count twelve equal pieces across the whole and eight shaded pieces.
Write 2/3 = (2 × 4)/(3 × 4) = 8/12.
Result: Each third becomes four twelfths; two shaded thirds become eight shaded twelfths.
Teaching notes
Listen for this difficulty: Changing fraction labels without connecting them to unchanged area.
Try this response: Keep the original shaded boundary visible while adding the new lines.
Look for:
Keeps the same whole and shading.
Uses the same factor for both counts.
2 A student says 6/8 = 3/8 after grouping shaded pieces in pairs. Repair the reasoning.
Start with eight equal parts, six shaded.
Group every pair of neighboring eighths into one fourth.
The whole has four groups and the shaded region has three groups.
Divide both counts by 2 to write 6/8 = 3/4.
Result: 6/8 = 3/4. Group all eight eighths in pairs, not only the shaded six.
Teaching notes
Listen for this difficulty: Regrouping the shaded pieces while retaining the old total count.
Try this response: Circle pairs throughout the entire strip, including the unshaded region.
Look for:
Changes both counts by division by 2.
Explains why the new denominator is 4.
3 · Guided practice
Choose three tasks
Mix a calculation or drawing with an explanation or error repair. Keep the other tasks for another short session.
1 Split each fourth in a 3/4 strip into two equal parts. Write the new fraction.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 6/8.
Listen for this difficulty: Leaving the shaded count as 3.
Try this response: Count the two smaller pieces in each of the three shaded fourths.
Look for:
Counts six shaded eighths.
Keeps the shaded boundary fixed.
2 Complete 1/3 = 4/__. Explain your factor.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 4/12, using a factor of 4.
Listen for this difficulty: Using different factors for numerator and denominator.
Try this response: Ask how many smaller pieces replace each original third.
Look for:
Writes denominator 12.
Uses factor 4 for both counts.
3 Repair the statement 1/3 = 2/4. Give a true equivalent fraction with numerator 2.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 1/3 = 2/6. Splitting each third in half creates sixths.
Listen for this difficulty: Adding one to numerator and denominator.
Try this response: Draw thirds and halves on equal strips to expose the changed amount.
Look for:
Rejects 2/4.
Supplies 2/6 with the same factor on both counts.
4 Group a strip with 8 of 12 equal parts shaded into groups of four small parts. Name the shaded fraction using the larger parts.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 2/3.
Listen for this difficulty: Dividing only the numerator when regrouping.
Try this response: Mark three groups of four across the whole and count the two shaded groups.
Look for:
Forms three equal larger parts.
Names two shaded groups out of three.
5 Are 3/6 and 2/4 equivalent? Explain using a common familiar fraction.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: Yes. Both equal 1/2.
Listen for this difficulty: Believing equivalence requires one numerator to be an integer multiple of the other.
Try this response: Group each strip into two equal regions and compare the shaded halves.
Look for:
Identifies both as 1/2.
Uses the same whole for the comparison.
6 Give two fractions equivalent to 2/3 with different denominators. Describe how you made each.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: Examples: 4/6 by multiplying both counts by 2, and 8/12 by multiplying both by 4.
Listen for this difficulty: Changing only the denominator to generate new names.
Try this response: Ask for the same split factor in every original third.
Look for:
Gives two valid equivalent fractions with distinct denominators.
Explains each common factor; other valid pairs count.
4 · Independent transfer
Try a fresh situation
Choose one task without coaching. Check the explanation against both criteria in its teaching notes; use the other task for a later check.
1 A recipe uses 3/4 cup. A cup measure is marked in twelfths. Which mark gives the same amount, and why?
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: 9/12 cup, because each fourth contains three twelfths.
Listen for this difficulty: Treating a finer scale as a different amount.
Try this response: Partition each fourth of a drawn cup scale into three intervals.
Look for:
Chooses 9/12 cup.
Explains the unchanged amount and factor 3.
2 Kai writes 2/3 = 4/5 because both numbers grew by 2. Explain the error and give a correct equivalent fraction with numerator 4.
Explain with a drawing, objects, or words.
Answer & teaching response
Answer or sample response: Adding 2 does not preserve the fraction. 2/3 = 4/6.
Listen for this difficulty: Assuming an equal additive change preserves a ratio.
Try this response: Split every third into two sixths and count both the shaded and total pieces.
Look for:
Rejects the add-two rule.
Gives 4/6 with a valid repartition or common-factor explanation.
What to do next
If the explanation holds: Continue when both counts change by the same factor and the student can explain the unchanged shaded boundary.
If the difficulty remains: Return to one shaded strip. Draw new lines through all original parts before writing any symbols.
Standards: 4.NF.A.1. Grade 4 alignment describes the mathematical work in this pack.
The tasks, worked examples, and teacher responses are original Fraction Classroom materials, version 2.0.0. The teaching approach draws on noticing the unit, moving between representations, and responding to student reasoning in the linked Illustrative Mathematics lesson. Its text and exercises are not reproduced here.