5.4 Small Group · Group 1
Tier 2 Intervention · Concrete-Representational-Abstract (CRA) · Dual-Language Anchors
Area of Composite Figures · Composite Figure · Procedural Fluency · Real-World Applications
- A composite figure is a shape made of two or more simple shapes joined together. We decompose it into basic shapes, find each area, then add or subtract. We'll walk through a worked example, try one together, then you'll try a few with hints right there when you need them.
- My L-shaped room splits into two rectangles: one is 12 ft by 8 ft, the other is 6 ft by 5 ft.
- First rectangle: A = length × width = 12 × 8 = 96 square feet.
- Second rectangle: A = 6 × 5 = 30 square feet.
- The pieces are joined, so I add: 96 + 30 = 126.
- So the total area is 126 square feet.
- Area of Composite Figures (Área de figuras compuestas) — The total space inside a figure made of basic shapes. Formula: A = A₁ + A₂ — add the parts (or subtract a missing piece).
- Composite Figure (Figura compuesta) — A shape made by putting two or more simple shapes together.
- Decompose (Descomponer) — To break a shape into smaller, simpler shapes.
- Add (Sumar) — Add up the areas of the smaller shapes to get the total.
- Subtract (Restar) — Take away the area of a missing piece from a bigger shape.
- Formula (Fórmula) — A math rule written with symbols.
- A common mistake in Area of Composite Figures is adding every piece even when a piece has been cut out of the figure. For a 10 ft by 8 ft rectangle with a 3 ft by 2 ft rectangular notch cut from one corner, students compute the full rectangle 10 × 8 = 80 sq ft and stop, or they add the notch instead of removing it (80 + 6 = 86 sq ft) instead of subtracting it: 80 − (3 × 2) = 80 − 6 = 74 sq ft. Before submitting, check whether each piece is part of the figure (add it) or missing from the figure (subtract it).
-
1 DRAG SORT
Sort each composite figure by whether you ADD or SUBTRACT the areas to find the total.
-
2 FILL TABLE
Solve the mathematical problem. Show all of your work and reasoning.
Figure Shape 1 Area Shape 2 Area Operation Total Area L-shaped deck Floor with alcove Wall with window cutout Courtyard with fountain cutout ✏️ Scratchpad / Reasoning
-
3 MULTIPLE CHOICE
An L-shaped room is made of two rectangles: 10 ft × 6 ft and 4 ft × 3 ft. What is the total area?
- A72 sq ft
- B60 sq ft
- C12 sq ft
- D72 ft
FormulaPut the numbers inWork it outAnswer with its unit- 1Name itWhich measure is asked?
- 2Write the formulaBefore any numbers.
- 3SubstituteMatch each letter.
- 4Unitunits, sq units, or cubic?
-
4 MULTIPLE CHOICE
A rectangular patio is 15 ft × 10 ft with a 5 ft × 4 ft rectangular flower bed cut out. What is the remaining area?
- A130 sq ft
- B150 sq ft
- C20 sq ft
- D170 sq ft
FormulaPut the numbers inWork it outAnswer with its unit- 1Name itWhich measure is asked?
- 2Write the formulaBefore any numbers.
- 3SubstituteMatch each letter.
- 4Unitunits, sq units, or cubic?
-
5 MULTIPLE CHOICE
Find the area of an L-shape made of a 5×3 rectangle and a 2×4 rectangle.
- A23 sq units
- B15 sq units
- C8 sq units
- D20 sq units
FormulaPut the numbers inWork it outAnswer with its unit- 1Name itWhich measure is asked?
- 2Write the formulaBefore any numbers.
- 3SubstituteMatch each letter.
- 4Unitunits, sq units, or cubic?
-
6 MULTIPLE CHOICE
When should you subtract areas instead of adding them to find the area of a composite figure?
- AWhen a piece is cut out or removed from a larger shape
- BWhen the shapes overlap
- CWhen one shape is larger than the other
- DAlways subtract — never add
✏️ Workspace & Solution Steps
Group Discussion Prompt: How does your visual model justify your mathematical solution?
Partner A: "I modeled this by identifying the relationship and..."
Partner B: "I agree with your step because the standard mathematical rule states..."
Complete each sentence stem to demonstrate precise mathematical reasoning:
Writing Task: Justify why your mathematical solution is accurate and complete.