Mathematics
Grade 7
15 min
Area of complex figures (Advanced)
Area of complex figures (Advanced)
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1
Introduction & Learning Objectives
Learning Objectives
Identify and classify basic geometric shapes within complex figures.
Apply the decomposition method to break down complex figures into simpler, familiar shapes (rectangles, triangles, parallelograms, trapezoids).
Apply the subtraction method to find the area of complex figures by removing a simpler shape from a larger one.
Calculate missing side lengths of complex figures using given dimensions.
Accurately calculate the area of each component shape.
Sum or subtract the areas of component shapes to find the total area of the complex figure.
Solve real-world problems involving the area of complex figures.
Ever wondered how much paint you'd need for a uniquely shaped wall, or how much carpet for a room with unusual corners? 🎨
In this lesson, you...
2
Key Concepts & Vocabulary
TermDefinitionExample
Complex FigureA polygon or shape that cannot be classified as a single basic geometric shape (like a rectangle or triangle).An L-shaped room, a cross-shaped swimming pool, or a house outline with a triangular roof.
Composite FigureAnother term for a complex figure, indicating it is 'composed' of two or more basic geometric shapes.A figure made by joining a rectangle and a triangle.
Decomposition MethodA strategy for finding the area of a complex figure by dividing it into simpler, non-overlapping basic shapes whose areas can be calculated individually.Splitting an L-shaped figure into two rectangles by drawing a line.
Subtraction MethodA strategy for finding the area of a complex figure by enclosing it within a larger, simpler shape and then subtracting the...
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Core Formulas
Area of a Rectangle
$A = l \times w$
Used to find the area of rectangular parts within a complex figure, where $l$ is length and $w$ is width.
Area of a Triangle
$A = \frac{1}{2} \times b \times h$
Used to find the area of triangular parts within a complex figure, where $b$ is the base and $h$ is the perpendicular height.
Area of a Parallelogram
$A = b \times h$
Used to find the area of parallelogram parts within a complex figure, where $b$ is the base and $h$ is the perpendicular height.
Area of a Complex Figure (General Principle)
$A_{complex} = A_{part1} + A_{part2} + ...$ OR $A_{complex} = A_{larger} - A_{removed}$
The total area of a complex figure is found by summing the areas of its decomposed parts or by subtracting the area of a 'missing' p...
5 more steps in this tutorial
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Easy
According to the tutorial, which statement best defines the 'Decomposition Method' for finding the area of a complex figure?
A.Subtracting the area of a small shape from a larger enclosing shape.
B.Dividing the complex figure into simpler, familiar shapes and summing their areas.
C.Finding the perimeter of the figure and multiplying it by the height.
D.Using a single, complex formula to calculate the area directly.
Easy
Which formula is used to calculate the area of a trapezoid, a shape that might be part of a complex figure?
A.= b × h
B.= l × w
C.= 1/2 × b × h
D.= 1/2 × (b1 + b2) × h
Easy
Following the 'House Outline' example, what is the total area of a figure composed of a rectangle with a length of 10 units and a height of 6 units, and a triangle on top that shares the 10-unit base and has a height of 4 units?
A.60 square units
B.20 square units
C.80 square units
D.100 square units
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