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  • Calculating the Area of Rectangles

  • Understanding Areas: Measurement in Square Units

  • Problem Examples: Rectangle Areas

  • Area Computations with Fractional Dimensions

  • Rectangles: Perimeter and Area Insights

  • Essential Rectangular Area Insights

Home > Resources > Calculate the Area of Rectangles: Examples with Formula & Fractions

Calculate the Area of Rectangles: Examples with Formula & Fractions

A rectangle represents a specific kind of a four-sided plane structure with every one of its four internal corners forming right angles. Instances of rectangles include a book, a sports ground, a pane of glass, and a piece of luggage meant for traveling.

Imagine you are interested in figuring out the entire area occupied by a sports ground. You would then need to understand the method for calculating the area of such a shape.

A quadrilateral whose internal corners are all right angles is defined as a rectangle. The rectangle's occupied two-dimensional extent is known as its area.

Defined as a quadrilateral where each pair of opposite sides runs parallel, a parallelogram has rectangle as its subset due to the perpendicular nature of its corners, making its opposite side pairs parallel. Hence, a rectangle is a parallelogram of a specific form.

Calculating the Area of Rectangles

To determine the area enclosed within a rectangle, multiply its length by its width. This multiplicative process reveals the rectangle’s area. This calculation involves the product of the rectangle’s length and its width. Below is an illustrative figure.

Demystifying Area Calculation for the Rectangle with an illustrative guide

The formula to arrive at the rectangle's area is:

\[Area = b \times h\]

where b denotes the base length, and h stands for the height length

In this geometrical setting, b symbolizes the length of edge AB, which is the base. It is usual to select one of the rectangle's lengthier sides as the base and a perpendicular side as the height. Within this rectangle, AD's length is aligned with the height.

Occasionally, the terms 'base' and 'height' might interchangeably be used for referring to the rectangle's length and breadth.

Specific Scenario: Calculating the Area of a Square

A square is a rectangle with the distinction that all four of its sides are equal in length and every internal angle measures 90 degrees.

Visual demonstration of calculating a square's area.

From the visual example, we recall the rectangle area formula: \[Area = base \times height.\]

As a square's all sides are equal, its base and height are the same. Thus, with knowledge of one side's length, one can determine its area, simplifying the formula to:

\[Area = side\,length \times side\,length = (side\,length)^2\]

Understanding Areas: Measurement in Square Units

Considering the area of shapes, it's critical to measure area in square units such as square centimeters (cm2), square feet (ft2), square inches (in2), amongst others.

To grasp square unit measurement, visualize how many square units would perfectly fill the shape's surface. This total represents the shape's area.

Square units as explained in Jurgensen & BrownGeometry

Problem Examples: Rectangle Areas

Below examples illustrate the process of determining the area of rectangles.

Example 1: Given a rectangle of 10 units by 5 units in dimension. The area is found by:

\[Area=10\,units\times5\, units=50\, square\, units\]

Example 2: For a garden shaped as a rectangle measuring 15 meters by 8 meters. The area is calculated as:

\[Area=15\,meters\times8\, meters=120\, square\, meters\]

Example 3: A rectangular pool with dimensions of 25 meters by 10 meters. The area, thus, is:

\[Area=25\,meters\times10\, meters=250\, square\, meters\]

Detailed explanation on rectangle area calculation:

A rectangle with an area of 60 m2 has a base measuring 20 m. The rectangle's height is?


Area = b × h

⇒60 m2 = 20 m × h

⇒ h = 60 m2 / 20 m

⇒ h = 3 m

When provided with a rectangle's side (base or height) and the diagonal's length, you can pinpoint the unknown side (height or base) using Pythagoras' Theorem, which asserts the hypotenuse square in a right triangle equals the sum of the squares on the other two sides.

This diagram exemplifies how a rectangle’s diagonal creates two right triangles, permitting the use of Pythagoras' Theorem. With knowledge of both base and height, calculating the area is straightforward.

Division by the diagonal results in two right-angle triangles within the rectangle.

In the depicted rectangle ABCD, with AB = 9 and BD = 15. Determine the surface area.


As rectangle corners are right angles, BD serves as the hypotenuse for right triangle ΔABD.


Through Pythagorean Theorem aplicability, \(AD^2 + AB^2 \Rightarrow AD^2 + 9^2 = 15^2 \Rightarrow AD^2 = 15^2 - 9^2 \Rightarrow AD^2 = 144 \Rightarrow AD = 12 \)

Rectangle area = b × h

= 12 ft. × 9 ft.

= 108 ft2

Considering a square with each side measuring 10 ft. The square's area calculation is?


Area = side × side

= 10 ft. × 10 ft.

= 100 ft2

Area Computations with Fractional Dimensions

Even if a rectangle's dimensions are fractional, its area can yet be ascertained by multiplying these fractions together.

Exploratory example:

Assuming a rectangle’s length \( b \) is \( \frac{3}{4} \) units while its width \( h \) spans \( \frac{2}{5} \) units.

To discover rectangle’s area \( A \): \( A = b \times h \) Inputting given fractionals: \( A = \frac{3}{4} \times \frac{2}{5} \) Multiplying fractions entails: \begin{align*} \text{Numerators product:} & \quad 3 \times 2 = 6 \\ \text{Denominators product:} & \quad 4 \times 5 = 20 \\ \end{align*} Yielding: \( A = \frac{6}{20} \) Simplification through greatest common divisor application: \( A = \frac{3}{10} \) Summarizing, rectangle's area presents as \( \frac{3}{10} \) square units.

Rectangles: Perimeter and Area Insights

Two essential rectangle properties encompass the perimeter and area.

Rectangle Perimeter: Defined as the outline’s total length, or sum of all sides. Given rectangles have pairs of equal lengths, perimeter \(P\) derives from: \(P=2l+2w\)

For instance, with dimensions of 5 units by 3 units, the perimeter computes as

\(2(5)+2(3) = 10+6 = 16\,units \)

In conclusion:

  • The area accounts for the inner space of the rectangle, quantifiable in square units (e.g., square centimeters, square meters, square inches).
  • The perimeter sums the external boundary's span, expressed in units of length (e.g., centimeters, meters, inches).

Essential Rectangular Area Insights

  • Defined, a rectangle is a quadrilateral with each internal angle totaling 90 degrees.
  • The rectangle area formula stands as: Area = base × height
  • A square represents a rectangle variant with uniformly equal sides.
  • A square’s area derives from: Area = side × side
  • Handling fractions necessitates their multiplication for area determination in rectangles.

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