The Cone and Cylinder Debate!

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Written by Holly (Teach Starter)

For over a year now, the Teach Starter team have been debating how to label the properties of a cone and cylinder. Who would have thought 3D objects would be so controversial?

Most of us were taught that cones and cylinders have edges and faces!

However, this has changed and there is a mathematical reason behind this change!

The NSW Syllabus outlines it very clearly:

  • In geometry, the term ‘face’ refers to a flat surface with only straight edges, as in prisms and pyramids, eg. a cube has six faces.
  • Curved surfaces, such as those found in cylinders, cones, and spheres, are not classified as ‘faces’.
  • Similarly, flat surfaces with curved boundaries, such as the circular surfaces of cylinders and cones, are not ‘faces’.
  • In geometry, the term ‘edge’ refers to the interval (straight line) formed where two faces of a three-dimensional object meet.
  • The NSW Syllabus describes a cylinder as a 3D object that has two flat surfaces, one curved surface, no faces, no edges and no vertices.

What are your thoughts? Does your school do something different?


Comments & feedback

  • Elisabet Kovacevic

    So pleased the labeling of these 3D objects has been brought to everyone’s attention. Many available resources don’t apply the correct terms.

    Comment by Elisabet Kovacevic on March 30, 2017 at 1:18 pm


    • Holly (Teach Starter) Holly (Teach Starter)

      Thanks for your comment Elizabet!
      Kind regards,
      Holly

      Official comment by Holly (Teach Starter) on March 30, 2017 at 1:22 pm


  • Sharon Hayman

    Thanks for the correct terminology ! its great to have resources that reflect the current information.

    Comment by Sharon Hayman on March 31, 2017 at 2:06 pm


    • Holly (Teach Starter) Holly (Teach Starter)

      Thanks for your comment Sharon 🙂

      Official comment by Holly (Teach Starter) on May 20, 2017 at 12:37 pm


  • Polly Alexander

    The posters in your shape set still have a sphere as having one face… given what you have decided above does this need to be updated?

    Comment by Polly Alexander on February 28, 2018 at 8:23 am


    • Holly (Teach Starter) Holly (Teach Starter)

      Hi Polly,
      Thanks so much for notifying us of this. We have now updated that resource to reflect the information in this blog. Have a lovely day!

      Official comment by Holly (Teach Starter) on February 28, 2018 at 8:52 am


  • Marcelino Simamora

    When I did my teaching, I found also confusing with cone and cylinder. No edges and vertices ? and only faces?

    Comment by Marcelino Simamora on July 31, 2018 at 6:33 am


    • Kristian Kristian

      Hi Marcelino,
      I am glad this blog could help you with defining the properties of these two objects.
      If there is anything else we can assist you with, please don’t hesitate to contact me.

      Official comment by Kristian on August 10, 2018 at 10:09 am


  • Alba Aparicio

    So is the point of the cone a vertex or apex? Cheers

    Comment by Alba Aparicio on September 7, 2018 at 6:53 am


    • Holly (Teach Starter) Holly (Teach Starter)

      Hi Alba, I believe it’s an apex.

      Official comment by Holly (Teach Starter) on September 14, 2018 at 6:55 am


    • Tracey Keynes

      I am wondering the same thing. I thought Apec and vertex were the same thing, but does the cone have one if it does not have edges? I think the answer is “no”.

      Comment by Tracey Keynes on May 6, 2019 at 9:09 am


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