4.9.11

Surface Area & Composite Shapes

Test yourself

Surface Area of 3D Shapes

The surface area of a 3D shape is the total area of all its surfaces. For a shape with only flat faces, calculate the area of each face individually then add them together.

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Cube

  • A cube of side length 3cm has 6 faces each with area 9cm2 so the total surface area is 54cm2.
  • Drawing a net can be helpful for calculating the total area.
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Sphere

  • The surface area of a sphere is:
    • Area = 4πr2
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Cylinder

  • The surface area of a cylinder is: Area = 2πrh + 2πr2
  • The length of the rectangular surface is the circumference of the base.
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Cone

  • The surface of a cone is: Area = πrL + πr2
  • Where L is the slant height.

Composite Shapes

A composite shape is formed when we glue two or more shapes together.

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Volume

  • When two solids are glued together into a composite solid, add the volumes together.
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Surface area

  • When two 3D shapes are glued together to form a composite, the glued faces should not be included in the surface area.
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Surface area - example

  • If we glue two cubes of side length 3cm together along one face the total surface area is:
    • 10 × 9cm2 = 90cm2
  • Since there are 12 faces total, but two are not on the outside of the object.

Jump to other topics

1Number

1.1Using Numbers

1.2Fractions, Decimals & Percentages

1.3Powers & Roots

1.4Accuracy

2Algebra

2.1Introduction to Algebra

2.2Manipulating Algebra

2.3Proofs & Functions

2.4Straight Line Graphs

2.5Common Graphs

2.6Transformations & Tangents

2.7Properties of Graphs

2.8Solving Equations

2.9Inequalities

2.10Sequences

3Ratio

4Geometry

4.1Introduction to Geometry

4.2Triangles & Quadrilaterals

4.3Transformations

4.4Circle Basics

4.5Circle Theorems

4.6Measurements & Units

4.7Calculating Area

4.8Triangle Formulae

4.93D Shapes

4.10Vectors

5Probability

6Statistics

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