SAT Surface Area: Definition, Formulas, Units for Shapes & Applications

Surface area is a mathematical concept that goes far beyond the classroom. Whether you're test-prepping with the SAT, ACT, GRE, or GMAT—or solving engineering, architecture, or physics problems—surface area is important to know. It assists in estimating the total exposed surface area of an object, ranging from easy-to-understand two-dimensional objects to complex three-dimensional objects. Mastering surface area formulas not only sharpens problem-solving skills but also enhances real-world applications in fields like design, manufacturing, and scientific research. In this guide, we’ll break down surface area, explore essential formulas, and highlight its diverse applications across different industries.

What is the Surface Area?

The surface area of an object refers to the total measure of all the areas covered by its surfaces. Within geometry, various three-dimensional shapes have distinct surface areas, and we will look into the methods of calculating these areas using specific formulas explored throughout this article. 

Surface area can be categorized into two main classifications, each carrying its own significance and applications.

• Lateral Surface Area or Curved Surface Area
• Total Surface Area

Understanding and calculating the surface area of a shape from its net involves a straightforward process. The net of a shape is a 2-dimensional representation of the shape that, when folded along its edges, forms the 3-dimensional object. Here's how you can determine the surface area using the net:

• Identify the individual faces of the shape from the net. Each face corresponds to a separate component of the 3-dimensional object.
• Measure the dimensions of each face, such as length, width, and height, using a ruler or measuring tool.
• Calculate the area of each face using the appropriate formula, depending on the shape. For example:
• Square or rectangle: .
• Triangle:
• Circle:

• Sum up the areas of all the individual faces to obtain the total surface area of the shape.

To provide a visual example, let's consider the net of a cube. The cube has six identical square faces, as shown in the image below:

By measuring the length of one side of the square face and applying the formula for the area of a square (), you can determine the area of one face. Multiply this area by six (since there are six faces) to obtain the total surface area of the cube.

Not every arrangement of six squares on paper produces a net for a cube. For example, a row of six squares does not fold to form a cube.

Surface Area Formulas

Every geometric figure has a specific formula to determine the surface area. In this section, we are going to learn about the formulas to determine the surface area of different objects. Total surface area encompasses all the faces of a 3D shape, including both flat and curved surfaces, while the lateral surface area specifically measures the curved surface area, excluding the bases. An example of a 3D figure with only a single curved surface and no flat base is a sphere. Take a look at the table provided below, which presents the surface area formulas for various three-dimensional shapes. 

Shape	Total Surface Area (TSA)	Lateral Surface Area (LSA) / Curved Surface Area
Cube	6a^{2}	4a^{2}, where aaa is the side length
Cuboid	2(lw+wh+lh)	2h(l+w), where l, w, and h are the length, width, and height
Cone	πr(r+l)	πrl, where r is the radius and l is the slant height
Cylinder	2πr(r+h)	2πrh, where r is the radius and h is the height
Sphere	4\pi r^{2}	Not applicable
Hemisphere	3\pi r^{2}	2πr2, where r is the radius
Square	a^{2}	Not applicable (2D shape)
Rectangle	w.h	Not applicable (2D shape)
Parallelogram	b.h	Not applicable (2D shape)
Trapezoid	1/2(a+b).h	Not applicable (2D shape)
Circle	π r2	Not applicable (2D shape)
Ellipse	π a.b	Not applicable (2D shape)
Triangle	1/2 * b * h	Not applicable (2D shape)

We have previously covered the two types of surface areas pertaining to three-dimensional shapes: total surface area and curved/lateral surface area. The total surface area encompasses the combined area of all the faces of the shape, whereas the curved or lateral surface area focuses solely on the area of the side faces. 

To gain a better understanding of the distinction, let's examine the cylinder provided below as an example.

Surface Area of Prism

A prism is a three-dimensional solid composed of two congruent polygonal bases and congruent rectangular lateral faces. A prism encompasses two distinct types of surface areas: the lateral surface area and the total surface area. The lateral surface area of a prism is calculated by summing the areas of all its lateral faces, while the total surface area is determined by adding the lateral surface area to the area of its bases.

• The lateral surface area of a prism = base perimeter height.
• The total surface area of a prism = Lateral surface area of prism + area of the two bases = ( Base Area) + Lateral surface area = ( Base Area) + (Base perimeter height).

Prisms come in seven different types, each distinguished by the shape of its bases. As the bases vary, so do the formulas used to calculate the surface area of each prism. Refer to the table provided below.

Shape	Base	Surface Area of Prism = (2 Base Area) + (Base perimeter height)
Triangular Prism	Triangle	Surface area of triangular prism
Square Prism	Square	Surface area of square prism
Rectangular Prism	Rectangle	Surface area of rectangular prism
Trapezoidal Prism	Trapezoid	Surface area of trapezoidal prism
Pentagonal Prism	Pentagon	Surface area of pentagonal prism
Hexagonal Prism	Hexagon	Surface area of hexagonal prism
Octagonal Prism	Octagon	Surface area of octagonal prism

The total surface area of a pyramid is found by adding the area of all the faces. A pyramid is a solid shape having a polygonal base and triangular lateral faces meeting at a common point known as the apex (or vertex). The distance from the apex to the center of the base, which is perpendicular, is referred to as the altitude (or height), whereas the perpendicular from the apex to the base of a triangular face is termed the slant height. It is very important to learn the surface area of a pyramid to solve geometry problems in competitive exams as well as in the practical application of architecture and engineering. Let us find out the formulas, derivations, and techniques to compute the surface area of pyramids.

What is the Surface Area of a Pyramid?

The surface area of a pyramid is the total area occupied by all its faces. It is measured in square units etc. A pyramid has two types of surface areas:

1. Lateral Surface Area (LSA): The sum of the areas of the triangular side faces.
2. Total Surface Area (TSA): The sum of the lateral surface area and the base area.

LSA of a Pyramid: \text{LSA of a pyramid} = \frac{1}{2} P l 

TSA of a pyramid=LSA+Base Area=

1/2 Pl+B

Where:

• P = Perimeter of the base
• B = Base area
• l = Slant height

Types of Pyramids and Their Surface Area

Various pyramids have varying base shapes, and their surface area calculation is different. Let's see the most prevalent ones.

1. Surface Area of a Square Pyramid

A square pyramid has a square base and four triangular side faces.

Formula:

• Base Area = a^2
• Base Perimeter = 4a 
• Total Surface Area =2al + a^2

TSA=a2+2al\text{TSA} = a^2 + 2alTSA=a2+2al

Where:

• a = Side length of the square base
• l= Slant height

2. Surface Area of a Triangular Pyramid (Tetrahedron)

A triangular pyramid (or tetrahedron) has a triangular base and three triangular faces.

Formula:

• Base Area = B
• Lateral Surface Area = Sum of areas of 3 triangular faces
• Total Surface Area = B+ sum of three triangular faces

TSA=B+∑(area of triangular faces)\text{TSA} = B + \sum \text{(area of triangular faces)}TSA=B+∑(area of triangular faces)

For a regular tetrahedron (equilateral triangles):

TSA=3a2\text{TSA} = \sqrt{3} a^2TSA=3a2

Where aaa is the side length of each triangle.

3. Surface Area of a Rectangular Pyramid

A rectangular pyramid has a rectangular base and four triangular faces.

Formula:

• Base Area = l×wl \times wl×w
• Base Perimeter = 2(l+w)2(l + w)2(l+w)
• Lateral Surface Area = 12Pl=12(2(l+w))l=(l+w)l\frac{1}{2} P l = \frac{1}{2} (2(l + w)) l = (l + w) l21Pl=21(2(l+w))l=(l+w)l
• Total Surface Area = lw+(l+w)llw + (l + w) llw+(l+w)l

TSA=lw+(l+w)l\text{TSA} = lw + (l + w) lTSA=lw+(l+w)l

Where:

• l = Length of the base
• w = Width of the base
• h= Slant height

Real-World Applications of Surface Area

Some of the real-world applications of surface area are listed below:

• Architecture and Construction: Surface area calculations play important roles in the estimation of material requirements, the maximization of cost-effectiveness, and the institution of structural integrity in construction.
• Engineering and Manufacturing: Surface area analysis helps engineers design efficient heat transfer systems, test structural endurance, and optimize manufacturing processes.
• Packaging and Material Estimation: Calculation of surface area aids in the estimation of packaging requirement, minimizing waste, and maximizing the use of packaging and shipping resources.
• Environmental Science and Biology: Surface areas are of pivotal importance in viewing biological structures, studying the absorption rates, and investigating ecological interactions across disciplines such as environmental science and biology.
• Art and Design: Surface area considerations affect art activities like the choice of canvas size, material usage in sculpture, and the optimization of visual beauty.
• Fluid Dynamics: Surface area affects fluid flow resistance, drag forces, and the design of efficient pipelines, channels, and fluidic devices.

These practical uses emphasize the significance of surface area in various fields, demonstrating its applicability beyond mathematical theory and its influence on real-life aspects of our existence.

Tips and Tricks on Surface Area

For tests like the SAT, ACT, GRE, and GMAT, surface area calculations are crucial to learn. These tests typically have questions that test your ability to use geometric formulas in a time-saving manner. The following are some useful tips and tricks to help you solve surface area problems with ease:

1. Learn the Important Formulas

Learn the surface area formulas of basic geometric figures such as Cube, Cuboid, Triangle , Rectangle, Hemisphere, Sphere etc. These are commonly asked in U.S. exams, so memorize them to save time during the test.

2. Decompose Complex Shapes into Simple Components

Most exam questions include composite shapes (e.g., a hemisphere with a cylinder). Decompose the shapes into their simple components, find their individual surface areas, and then add them together.

3. Use Symmetry

If the shape has symmetrical parts, determine one part's surface area and multiply it by the number of equal parts. This technique is particularly convenient for pyramids, prisms, and cylinders.

4. Visualize the Shape

In the case of word problems, draw the provided shape in order to have a better sense of its structure. This may assist in determining the faces that are included in the overall surface area.

5. Estimate When Necessary

Certain multiple-choice questions on tests such as the SAT and ACT do not demand precise calculations. Round numbers and estimate the surface area to eliminate wrong answer choices quickly.

6. Be Aware of Unit Conversions

Make sure all measurements are in the same unit before calculation. If they are given in mixed units (for example, inches and feet), convert all of them to one consistent system of units to prevent mistakes.

7. Look for Hidden Surfaces

Certain 3D shapes contain concealed faces that still count towards the overall surface area. Examine composite solids thoroughly to make sure all applicable surfaces are included.

8. Steer Clear of Common Pitfalls

Applying formulas incorrectly: Double-check that you're applying the right formula for the shape in question.

• Omitting curved surfaces: For cones and cylinders, include both flat and curved surfaces.
• Omitting missing faces in the subtraction: The shapes might have open sections (e.g., a hollow cylinder). Adjust the surface area correspondingly.

Surface Area Solved Examples

1.Calculate the surface area of a rectangular prism with dimensions of length cm, width cm, and height cm.

Solution:

The surface area of a rectangular prism can be calculated using the formula: .

Plugging in the given values:

Surface area

Therefore, the surface area of the rectangular prism is .

2.Find the surface area of a cylinder with a radius of cm and height of cm. (Take ).

Solution:

The surface area of a cylinder can be calculated using the formula: , where is the radius and is the height.

Plugging in the given values:

Surface area

Therefore, the surface area of the cylinder is .

3.Determine the surface area of a sphere with a radius of cm. (Take ).

Solution:

The surface area of a sphere can be calculated using the formula: , where is the radius.

Plugging in the given value:

Surface area

Therefore, the surface area of the sphere is approximately .

It is important to know surface area not just for competitive tests such as the SAT, ACT, GRE, and GMAT but also for real-life applications in engineering, architecture, and design. Understanding the formulas for surface area allows maximum utilization of materials, increases industrial process efficiency, and solves daily geometry problems. With simplification of complicated shapes, application of correct formulas, and utilization of estimation skills, students and professionals can enhance their problem-solving skills. A strong grasp of surface area provides accurate results for both exams and daily use. Keep listening to the Testbook App for more news and test series to improve preparation.

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