Thursday, 9 December 2010

Day Nine

Today a tutorial for making a decoration that will impress and amaze your family and friends... well perhaps not, but I needed to grab your attention somehow.

Long ago back in the days when I used to teach maths to classes of unruly fifteen year olds, this time of year always brought cries of "Not more algebra miss, can't we do something fun instead of lessons?" And this was always one of my standbys... mathematical, seasonal and fun... well I thought so!

You will need twenty old Christmas cards, a compass and pencil, a biro, a ruler, scissors and glue. Before you express amazement that I was organised enough to keep my Christmas cards from last year in order to make this year's decorations, let me put you right. The bag of old cards was discovered hanging on the back of a cupboard door where I had put them ready to be recycled...and then forgotten all about them all year. Needless to say it's a while since I cleared out that cupboard.

Anyway... back to the task. I used a radius (here comes the maths) of about 4cm which gives a finished decoration about 15 cm across. On the back of one of the cards draw a circle using the compass. Then placing the point of the compass on the circumference, draw an arc on the circumference as in the photo.

Move your compass, so that the point is now at the point where the arc cuts the circumference and draw another arc. Repeat around the circle until you have divided the circumference into six equal parts. This will only work if you are accurate in placing your compass and you do not change the radius.

With a biro, and pressing hard, join alternate arcs on the circumference to give an equilateral triangle (I hope you are impressed by the amount of maths I'm throwing in here). Then cut out your circle.


By pressing hard with the biro you will have also scored along the lines so they can be folded giving a triangle with flaps.

Which should look like this! Hands up everyone whose circle looks like this....

Now repeat nineteen more times so that you end up with twenty identical folded triangles.

The next step is to take five of your triangles and begin by glueing two of them together by their flaps.


At this stage it should look like this.

Continue glueing the remaining three triangles to the first pair so that you end up with something that looks a bit like a hat. Much easier to demonstrate than to explain!

Set your "hat" aside and repeat with another five triangles, this time trapping a ribbon loop in the apex, from which to hang your decoration.

Then glue the remaining ten triangles into a strip as shown below.

Join the strip of ten triangles into a ring by glueing the first and last flaps together.

Almost there... Now take one of your "hats" and glue it to the top of your ring, matching the flaps.


Turn it upside down and glue the remaining "hat" to the bottom of your ring, again matching the flaps.

And hey presto... your decoration... which just in case you were wondering is actually an icosahedron.
Of course by now my class of fifteen years olds would be having lots of non-mathematical fun, playing darts with the compasses and football with their icosahedra... but you are far too sensible.

If you are not as
slovenlyorganised as me and don't have a handy stash of old Christmas cards... any card will do and you could always spray the finished item gold if it doesn't look festive enough!

26 comments:

  1. ooh I remember making something similar to that when I was young, thanks for the tutorial, must get me and the kiddies making some.

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  2. I remember making these - I used to love them!

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  3. OMG, that takes me back. along with origami, I used to love making shapes like these.

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  4. This does look like fun...your tutorial is excellent!

    I'm going to look for a compass. I've got lots of suitable paper around here.

    xo

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  5. Oh er looks a bit complicated. But I'll give it a go over the weekend.

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  6. Brilliant idea for recycling old xmas cards ... they could be used AS cards too .. I wonder also if you could glue fabric to them, stick them together then put beads all along the edges .. hmm..

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  7. Oooh I made these very ornaments last year. But I cheated and used a Martha Stewart kit with pre-cut and scored circles (hangs head in shame).

    K x

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  8. I bet they loved you. I used to love my science teacher because at the end of term he would allow us to cut lengths of glass tubing, heat it in the flame of the bunsen burner and blow glass bubbles.........

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  9. I love it, maths was always my favourite subject at school and even yet I love any sort of number puzzles. This would be great fun to make. :)
    Vivienne x

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  10. I LOVE these Gina - as a draughtsman I love anything that puts geometry and craft together! I did have a go at one a few years ago - if not too cheeky you can see here: thepatchworkdress.typepad.com/the_patchwork_dress/2007/11/advent-adventur.html
    and cut up an old calendar - as they are getting towards end of usefulness, could be a way of using a much loved image? Ps posted off your cards, but our postal service a bit delayed, hope you get them soon Caireen x

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  11. Thanks for sharing this Gina - they look beautifully complicated when finished, but you make them sound achievable! I'll be bookmarking this ready for the end of next week when the school holidays start, then I'll be armed and ready when the 'I'm bored...' cry comes!

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  12. Memories! Did you ever make those school year calendars with your class? I still have one for the year August 73 to June 74 - no school in August in Scotland - in case I make one again! It is made from 12 pentagons in a similar way, but the flaps are stuck inside so that they can't be seen. I never did do it again, but they made super desk calendars. It would be so much easier now with computers - in those days, someone clever typed out the months so that each week had a straight side. I suspect a lot of the pupils just used them as funny shaped balls.

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  13. What a lovely decoration and your instructions are so clear that I think even I could follow them! I wish I'd had a maths teacher like you when I was at school.

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  14. I am exhausted reading the instructions...

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  15. Takes me right back to school. The maths teacher used to hide in the cupboard playing the sax. I'm sure we just played games and didn't end up with a fabmathulous bobble!

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  16. I'll save my Christmas cards and do this after Christmas!!!

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  17. Great tutorial. I am just going to fish out last year's cards - yes I do still have them, just in case!

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  18. Genius! And beautifully clear tutorial, too.

    Thanks, Gina!

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  19. Brilliant - another one to add to my 'to do' list x

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  20. You're so funny -- I'll bet it WILL amaze my friends and family. In fact, wouldn't they make fun little gifts!

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  21. I actually do have last year's cards- but do I have the patience and the time - where did I put the compass? They are brilliant thanks for the instructions.

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  22. OOH, I love this idea. Thanks, I failed maths many years ago but I think I can do this,
    cheers.

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  23. Going to have a go tomorrow and if you don't mind demo it to my Yr10 next Friday, during their last lesson. Thank you

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  24. I love the idea of this but don't think I could stand the pain - all that maths frightens me!

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  25. Such a fun teacher! I'll bet your class is remembered warmly by many of your students.

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  26. Totally and utterly brilliant. Thankyou - I'd always wondered how to make these!

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