Understanding Faces, Edges and Vertices Video Lecture | Mathematics for Grade 7

Hello welcome to MooMooMath In this video
I would like to talk about
Edges Vertices and Faces of a solid
Face the flat surface of a solid
Edge- where two faces meet
Vertices a point where two or more edges meet
If your solid is a rectangular solid then
you can use a simple formula to find the edges,
vertices, and Faces
Base + 2 = Number Faces
Base x 2 = Vertices
Base x 3 = Edges
This cube is a rectangular solid and has a
base of 4 sides
4 + 2 = 6 Number of Faces
4 x 2 = 8 Number of vertices
4 x 3 = 12 number of edges
Unfortunately you can’t use this for all
solids
There is another formula you can use for all
convex polyhedrons
It is called Eulers formula used in Geometry
states,
Face + Vertices – Edges = 2
Let’s look at some examples of Eulers Formula
Cube has 6 faces + 8 Vertices – 12 Edges
= 14-12=2
Octahedron 8 faces + 6 Vertices – 12 Edges
= 2
What about a cone?
How many faces, edges, and vertices does a
cone have?
What about cones and solid cylinders?
If you’re definition of a face will allow
for a curve, then the cone will have 2 face
and 1 edges
The solid cylinder will have two edges if
you allow the edge to be curved, and 3 faces
2 circle ones and a rectangle (if you take
the top and bottom off a tin can then cut
the cylinder part on the seam and flatten
it out you would get a rectangle). and no
vertices (no corners).