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How many sides do I tell my Y1s a circle has?

Discussion in 'Mathematics' started by star17, Oct 10, 2010.

  1. I have seen the debates on this site/others about how many sides a circle can be said to have. I do not want to teach my Y1s incorrectly but at the same time I do not want to confuse them so what do I say? A circle does not have any sides? It has one curved side? Please help! Thanks.

  2. The answer 2 (the in-side and the out-side) joke always worked for me! Well, the children liked it anyway!
  3. DM

    DM New commenter

    It depends on your definition of side.
    If you say a side is a straight line segment, then the answer is zero.
    If you define a side as a curved boundary, it could be one.
    If you think about a circle as a regular polygon with a very large number of sides, you might conclude the answer is infinite.
    I would just avoid using the word side in connection with a circle (in mathematics we do not favour side anyway, the preferred word is edge).
    The comedy answer is two sides, inside and outside.
  4. Now, on our round dinner table at home my wife sits on the other side of the table to me and when we have guests they sit either side of each other but not on the same side as either my wife or I.
  5. DM

    DM New commenter

    So how many guests need to turn up to your party before some end up on the same side (or sitting on someone's lap)?
  6. DM

    DM New commenter

    ... and why wasn't I invited?
  7. A regular polygon with a very large number of sides will only ever be an approximation of a circle, even if you reach an infinite number.

    A circle has one curved edge, no sides.
  8. what i hate about shapes with younger kids is that circles are lumped in with polygons and the traditional way of classifying them is that they have 1 side - bleurgh - i wish all ks1 shape work came in 2 types - polygons and shapes with curves
    as it doesn't, even in year 1, i think it's worth saying that 'sides' means 'straight sides' so it just isn't something we can say about a circle (or do you then say a semi-circle has 2 sides, a quadrant 3? )
    i suspect you then have the problem that sats - and other teachers - expect them to regurgitate the 1 side thing cos that's the way it's always been done (don't start me on ovals and ellipses)
    with my gat kids i do try to introduce the idea of circles as the limiting polygon ie it doesn't have an infinite number of sides or angles, but it is the infinite limit of an n-sided polygon in y5 or 6
    sometimes they get it, sometimes they don't
    one can but try
    my dining table is that locus-of-a-goat-tethered-to-a-rod shape, that as far as i know has no name, but should have (the shape of a rich tea finger). one of my y6's suggested 'circloid' - any improvements?
    it seats up to 8 - hmm - if i feel like a dinner party....
  9. Hmmmmmm ... I am still coming to terms with the fact that a cylinder is not a prism ... makes me cry
  10. tafkam

    tafkam Occasional commenter

    I quite liked "the shape a rich tea finger" [​IMG]

  11. but it is the infinite limit of an n-side-based prism - i think
    (it's late)
    tafkam - do you think we could get that into the textbooks?
  12. Sure ... but I always used to say it was a prism (and that a cone was a pyramid) ... then the NC made me stop

    SO now I have to say "acts like ... ... ... "
  13. DM

    DM New commenter

    Well you will be able to call it whatever you like again soon won't you?
  14. Oh you Bad Boy

  15. DM

    DM New commenter

    People pay large sums for this?
  16. Not Large to be honest but it can pay the bills (the phone bills usually)

    I am now trying to imagine a dominatrix saying "Say the cylinder is not a prism" with whip in hand
  17. This thread will definitely be one of the ones advertised on the weekly TES email now ...
  18. Andrew Jeffrey

    Andrew Jeffrey New commenter

    Just to make sure it does, did you read this morning's Daily Mail? Apparently Prisms can cause Cancer in illegal immigrants.
    Amazing what you learn from the quality press, I think.
  19. How is a cylinder not a prism? It's got a cross-section that looks the same wherever you chop it, that makes it a prism in my book.
  20. who says maths isn't fun
    erm - whoever asked - because the ends of the prism have to be joined up by rectangles
    Safia8 likes this.

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