4.19.11

Surface Area & Composite Shapes

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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.

Cube

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.
Sphere

Sphere

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

Cylinder

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

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.

Volume

Volume

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

Surface area

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

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
1

Number

1.1

Place Value & Ordering

1.2

Numerical Operations

1.3

Structure of Calculations

1.4

Fractions

1.5

Numerical Operations on Fractions

1.6

Roots & Powers

1.7

Numerical Skills

1.8

Factors & Multiples

1.9

Surds

1.10

Standard Form

1.11

Fractions, Decimals & Percentages

1.12

Percentage Change

1.13

Rounding & Estimation

1.14

Bounds & Accuracy

1.15

Using Numbers

1.16

Fractions, Decimals & Percentages

1.17

Powers & Roots

1.18

Accuracy

2

Algebra

2.1

Algebraic Notation

2.2

Substitution & Simplification

2.3

Brackets

2.4

Algebraic Fractions

2.5

Rearranging

2.6

Functions

2.7

Solving Linear Equations

2.8

Inequalities

2.9

Solving Quadratic Equations

2.10

Simultaneous Equations

2.11

Iteration

2.12

Sequences

2.13

Linear Graphs

2.14

Introduction to Algebra

2.15

Manipulating Algebra

2.16

Proofs & Functions

2.17

Straight Line Graphs

2.18

Common Graphs

2.19

Transformations & Tangents

2.20

Properties of Graphs

2.21

Solving Equations

2.22

Inequalities

2.23

Sequences

3

Ratio

3.1

Unit Conversions

3.2

Compound Units

3.3

Ratio Fundamentals

3.4

Advanced Ratio and Scale

3.5

Proportion

3.6

Algebraic Proportion

3.7

Ratios in Practice

3.8

Manipulating Ratios

3.9

Percentage & Interest

3.10

Proportion

3.11

Gradient

4

Geometry

4.1

Area & Perimeter

4.2

Angles

4.3

Trigonometry

4.4

Similarity & Congruence

4.5

Circle Geometry

4.6

Circle Theorems

4.7

Pythagoras

4.8

Surface Area

4.9

Volume

4.10

Vectors

4.11

Introduction to Geometry

4.12

Triangles & Quadrilaterals

4.13

Transformations

4.14

Circle Basics

4.15

Circle Theorems

4.16

Measurements & Units

4.17

Calculating Area

4.18

Triangle Formulae

4.19

3D Shapes

4.20

Vectors

5

Probability

6

Statistics

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