Math CentralQuandaries & Queries


Question from Nick, a student:

A pyramid has 15 faces. What shape is its base and how many edges does it have?

Hi Nick,

Pyramids are named by the shape of the base. I have drawn a pentagonal pyramid, that is a pyramid with a pentagon as its base.


This pyramid has six faces, the base plus five triangles, one for each side of the base. This pyramid has 10 edges, you can just count them. Can you see why a pyramid with a pentagonal base will have 2 times 5 = 10 edges without counting them?

Can you now answer your question? If you want to know the name of the polygon that forms the base for your pyramid you can look in our list of polygon names.


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