Fraction Classroom
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Grade 5 · 15 minutes · Teacher-led small group

Find the overlapping part of a whole

Build a two-direction area model to connect fraction multiplication with overlap and square units.

Listen for the idea

The product counts the overlap of two selections, using the original whole as the reference area.

  • Partition a rectangle in two directions and identify only the overlap.
  • Connect the grid cell count to both factors and to the area unit.

Materials: Paper and ruler; Two colored pencils, or different hatch patterns.

A 15-minute route

  1. 3 minutes: Try the three diagnostic questions. Ask for a brief explanation.
  2. 3 minutes: Teach one worked example that addresses the difficulty.
  3. 6 minutes: Choose three practice tasks and discuss the reasoning.
  4. 3 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: Label the whole rectangle before adding a grid. Use vertical hatching for one factor and horizontal hatching for the other; count only the crosshatched cells for the product.

Open an interactive area model →

1 · Quick diagnosis

What does the explanation reveal?

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 whole rectangle has 3 equal columns and 4 equal rows. What fraction of the whole is one cell?

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 1/12, because the grid has 3 × 4 = 12 equal cells.

Listen for this difficulty: Adding row and column counts to get sevenths.

Try this response: Count three cells in each of four rows.

Look for:

  • Identifies 12 equal cells.
  • Names one cell as 1/12 of the whole.
After hearing the explanation

2 In a 3-column by 4-row grid, shade 2 columns vertically and 3 rows horizontally. How many cells have both shadings?

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 6 cells, in the 2-by-3 overlap.

Listen for this difficulty: Counting every cell with either shading instead of their overlap.

Try this response: Touch only cells crossed by both hatch directions.

Look for:

  • Counts 6 overlap cells.
  • Distinguishes overlap from the union of shaded regions.
After hearing the explanation

3 Should 1/2 × 2/3 be greater or smaller than 2/3? Explain the meaning of the first factor.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: Smaller. Taking one half of two thirds gives 1/3.

Listen for this difficulty: Assuming multiplication must increase a positive number.

Try this response: Start with two thirds shaded and keep only half of that area.

Look for:

  • Predicts smaller.
  • Interprets the first factor as taking a part of the second.
After hearing the explanation

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 Use an area model for 2/3 × 3/4.

  1. Draw one rectangle and label it one whole.
  2. Split it into three columns and select two.
  3. Split the same rectangle into four rows and select three.
  4. The overlap has 2 × 3 = 6 cells out of 3 × 4 = 12 equal cells; six twelfths is one half.

Result: 6/12 = 1/2 of the original whole.

Teaching notes

Listen for this difficulty: Counting only rows or using the shaded subregion as a new whole.

Try this response: Keep the outline of all twelve cells visible while counting the overlap.

Look for:

  • Counts six overlap cells out of twelve.
  • Names the original rectangle as the whole.

2 A rectangular mat is 3/4 meter long and 2/5 meter wide. Find its area with a unit-square model.

  1. Draw a 1 meter by 1 meter reference square.
  2. Divide its length into fourths and width into fifths, making twenty equal cells.
  3. Select three fourths in one direction and two fifths in the other.
  4. The mat occupies six cells, each 1/20 square meter, for an area of 3/10 square meter.

Result: 6/20 = 3/10 square meter.

Teaching notes

Listen for this difficulty: Giving a length unit for an area or adding the side fractions.

Try this response: Point to the two dimensions of a single cell and then to the square-meter reference whole.

Look for:

  • Uses multiplication for rectangular area.
  • Reports 3/10 square meter and explains twentieth-sized cells.

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 Draw a grid showing 1/2 × 3/5. Label the whole and count the overlap.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 3/10 of the whole; three overlap cells out of ten.

Listen for this difficulty: Counting five total cells because only one partition direction is noticed.

Try this response: Trace both the two columns and five rows across the full rectangle.

Look for:

  • Draws ten equal cells.
  • Identifies three overlapping cells.

2 A rectangle is divided into 4 columns and 3 rows. Two columns and one row are selected. Write the product and its value.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 2/4 × 1/3 = 2/12 = 1/6.

Listen for this difficulty: Treating two columns plus one row as three selected twelfths.

Try this response: Count the cells lying in both selections rather than adding the selection counts.

Look for:

  • Writes factors that match the selected dimensions.
  • Finds 1/6 from two overlap cells.

3 A student says 2/3 × 1/4 = 3/7 by adding both pairs of numbers. Explain using a grid.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: A 3-by-4 grid has 12 cells and the 2-by-1 overlap has 2 cells, so the product is 2/12 = 1/6.

Listen for this difficulty: Applying addition to the factors instead of counting a rectangular overlap.

Try this response: Count equal cells in the whole and in the overlap separately.

Look for:

  • Uses a 12-cell whole.
  • Finds a 2-cell overlap and 1/6.

4 Find the area of a rectangle measuring 2/3 meter by 1/2 meter. State the unit.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 1/3 square meter.

Listen for this difficulty: Reporting meters or interpreting multiplication as a perimeter calculation.

Try this response: Fit two of the six equal cells of a unit square into the rectangle.

Look for:

  • Finds 1/3.
  • Uses square meter as the unit.

5 Does switching 2/3 × 3/4 to 3/4 × 2/3 change the area? Explain by turning a grid.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: No. Rotating the rectangle exchanges rows and columns but keeps six overlap cells out of twelve.

Listen for this difficulty: Believing the first shading direction determines a different product.

Try this response: Rotate the paper a quarter turn and count the same cells.

Look for:

  • States equal products.
  • Explains the unchanged overlap under rotation.

6 A rectangle has 5 columns and 4 rows. An overlap covers 3 columns and 2 rows. Give its fraction of the whole in simplest form.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 6/20 = 3/10.

Listen for this difficulty: Using 3 + 2 for the numerator and 5 + 4 for the denominator.

Try this response: Count three cells in each of two overlap rows, then count all twenty cells.

Look for:

  • Counts 6 of 20 cells.
  • Simplifies to 3/10.

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 garden uses 3/4 of a rectangular plot. Herbs occupy 2/3 of the garden. What fraction of the entire plot contains herbs? Name both wholes in the story.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 1/2 of the entire plot. The garden is 3/4 of the plot, and the herbs are 2/3 of that garden: 2/3 × 3/4 = 6/12.

Listen for this difficulty: Treating the garden and entire plot as the same reference whole.

Try this response: Outline the plot first, then take two thirds only within the selected garden region.

Look for:

  • Finds 1/2 of the plot.
  • Distinguishes the plot whole from the garden subregion.

2 A sign has side lengths 5/6 meter and 3/4 meter. Find its area, then explain why the result is less than 5/6 square meter.

Explain with a drawing, objects, or words.

Answer & teaching response

Answer or sample response: 5/8 square meter, since 15/24 = 5/8. Its width is only 3/4 meter, so it fills less area than a 5/6-by-1-meter rectangle.

Listen for this difficulty: Assuming a product is larger than either positive factor.

Try this response: Compare the sign with the same-length rectangle of width 1 meter.

Look for:

  • Finds 5/8 square meter.
  • Uses a geometric comparison to explain the smaller area.

What to do next

If the explanation holds: Continue when the student names the original whole, counts only the overlap, and uses square units for rectangle area.

If the difficulty remains: Use 1/2 of 1/2 first. Fold one square twice in perpendicular directions and distinguish the double-selected quarter from all shaded regions.

Continue with a full lesson →

Materials for your group

Student pages and teacher answers are separate. Download an HTML file to keep or use your browser to print or save as PDF.

Standards & original sources

Standards: 5.NF.B.4.a, 5.NF.B.4.b. Grade 5 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.