Session 18 – 3D shapes

Basic 3D shapes  Discussion of  Nets  Isometric projection  Faces, edges and vertices  Ex30.1 on the board

3D Symmetry  Planes of symmetry  Axis if rotational symmetry  Ex 30.2 – 10 minutes

Plans and elevations  A plan view is to look down from above  An elevation is to look at an object from the front, back or side  In reality the drawings are usually done to scale and contain dimensions. (arrows labelling lengths)

Surface area  Consider every face of a 3D shape.  These could be drawn as a 2D shape, which we could then find the area of (using our knowledge from a few weeks ago)  Add up the area of each face for the total surface area.  For example, a cuboid is made up of rectangles and squares

Volume of a cuboid  The volume of a cuboid is found by multiplying all the lengths.  You could consider this as finding the area of one end, then multiplying by the length.  Ex30.4 – 10 minutes

Volume of a prism  A prism is a 3D shape, which is continuous all the way through.  Its volume is found by working out the area of the end face, and multiplying this by the length of the shape.  Ex 30.5 Q1,2 and 3

Surface area of a prism Total surface area of a prism is found by adding up the area of each face. For example, a triangular prism is made up of 2 identical triangular faces and 3 rectangular ones.

Surface area of a cylinder h

 Ex minutes  Foundation learners to go back over previous exercises for practice  Higher learners have more 3D shapes to work with

Cones and frustums

Pyramids  The formula for a pyramid is the same as for a cone. You must remember this link. The equations for cones are given but not for a pyramid  V = 1/3 x base area x height

Spheres

Homework  Use BKSB to revise topics  Produce a revision page for the geometry ‘what you need to knows’  Including 2D shapes, 3D shapes and circles