Mathematics
Grade 10
15 min
Area of rectangles and squares
Area of rectangles and squares
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1
Introduction & Learning Objectives
Learning Objectives
Calculate the area of rectangles and squares when dimensions are expressed as algebraic expressions.
Solve for unknown dimensions of a rectangle or square given its area and one other dimension, potentially involving solving linear or quadratic equations.
Calculate the area of a rectangle or square defined by vertices on a Cartesian plane.
Apply area formulas to solve multi-step word problems, including those involving unit conversions or composite shapes.
Use the Pythagorean theorem to find a missing dimension of a rectangle given its diagonal and one side, and then calculate its area.
Formulate a simple proof related to the area of rectangles or squares.
How does a GPS calculate the area of a rectangular park from satellite data? 🛰️ It all comes down to...
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Key Concepts & Vocabulary
TermDefinitionExample
AreaThe measure of the two-dimensional space enclosed by a shape. It is always expressed in square units (e.g., cm², m², square units).A floor tile that is 1 foot by 1 foot has an area of 1 square foot.
RectangleA quadrilateral with four right angles (90°). Opposite sides are equal in length and parallel.A standard sheet of A4 paper, a smartphone screen, or a door.
SquareA special type of rectangle where all four sides are equal in length. It also has four right angles.A single square on a chessboard or a standard wall tile.
DimensionsThe measurements that define the size of a shape. For a rectangle, these are its length and width. For a square, it is the side length.A rectangle might have dimensions of 5 meters by 3 meters.
Cartesian PlaneA two-dimensional coordinat...
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Core Formulas
Area of a Rectangle
A = l \times w
The area (A) of a rectangle is found by multiplying its length (l) by its width (w). Ensure both dimensions are in the same unit before multiplying.
Area of a Square
A = s^2
The area (A) of a square is found by squaring its side length (s). This is a special case of the rectangle formula where l = w = s.
Pythagorean Theorem (for finding dimensions)
l^2 + w^2 = d^2
In a rectangle, the length (l), width (w), and diagonal (d) form a right-angled triangle. This theorem can be used to find a missing side length if the other side and the diagonal are known.
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Challenging
A rectangle has a perimeter of 34 meters and an area of 60 square meters. What are its dimensions?
A.Length = 10 m, Width = 6 m
B.Length = 15 m, Width = 4 m
C.Length = 12 m, Width = 5 m
D.Length = 20 m, Width = 3 m
Challenging
The length of a rectangular plot is increased by 20% and its width is decreased by 10%. What is the net percentage change in the area of the plot?
A.10% increase
B.8% increase
C.12% increase
D.2% decrease
Challenging
Given a square with side length 'a' and a smaller square with side length 'b'. The difference in their areas, a² - b², can be represented geometrically by the area of a specific rectangle. What are the dimensions of this rectangle?
A.Length = (a - b), Width = (a + b)
B.Length = a, Width = (a - b)
C.Length = (a + b), Width = (a + b)
D.Length = 2a, Width = 2b
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