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## Geometry (all content)

### Unit 3: Lesson 6

Geometric solids (3D shapes)

# Recognizing common 3D shapes

Sal identifies the following 3D shapes: square pyramid, rectangular prism, triangular prism, cylinder, and cone.

## Want to join the conversation?

• how do i find surface area
• You find the area of each side of the object and then add them all together.
• Would a shape with an octagon for a base and triangles for sides meeting at a point be called an octagonal pyramid?
• Yes,an octagonal pyramid is a pyramid with a base that's a polygon with eight sides, or an octagon, and triangular faces, or sides, that meet at a point directly above the bottom.
• At , Sal says "This has sides that are triangles", doesn't he mean faces?
• I think he means bases.
• I don't know what a vertice is
• 頂点は、3つのエッジの交点です。 It is the intersection of three edges.
• what the differences between vertices and edges?
• A vertex is where two or more edges meet, so a vertex is a point and a edge is a line segment.
• Would a shape with an octagon for a base and triangles for sides meeting at a point be called an octagonal pyramid?
• Yes a pyramid has a single base and a vertex where all lateral edges meet. You always name a pyramid (and a prism) by the shape of the base.
• Which figure does not belong with the other three and explain if you have a triangle, cube, sphere, and cylinder
• It is the triangle because it isn't a 3 dimensional shape. If it is 3 dimensional, then it's the sphere because it has no edges.
• What kind of polygon have 100 sides ?
• Think of a century as 100 years, so it would be a centagon. This is like a decagon is like a decade (10 years).
• A sphere is a circle right?