Hula Hoops, String, Circles and pi

15 May

I was recently asked by a friend (OK, it was a tweet by the excellent @thought_weavers aimed at anyone at all ) for my thoughts on introducing circumference and area to a class of year 6 pupils.

I quite liked my reply so I thought I’d blog about it at is is nice and simple.


Hula hoops, Coins, String, Scissors, Cans of baked beans {or other}, Anything else of a circular nature. Cotton


Place various circular objects around the room along with scissors and string/cotton.

Split pupils into small groups or pairs and position them at an object.

Ask them to show where the diameter of the circle they have is. Then ask them to cut the string into a piece equal to the diameter.

Ask the question – how many times does the string fit areound the circle.

Investigate. Hopefully they will discover that it fits round just over three times (3.14 to be more precise, 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679 
  724587006606315588174881520920962829254091715364367892590360011330530548820466521384146951941511609 to be even more precise). That’s it, they have discovered pi.

That’s it really. Chance for pupils to investigate pi and see what it is and where it comes from. There are loads of worksheets and things for working out circumference and area but you can always explore a bit too with some tape measures etc – there are genrally plenty of circles to be found.

For pupils who forget how to calculate you could let them watch this (It will annoy them but stick in their heads):

Or this rhyme:

Tweedle dum and tweedle dee
Round the circle pi times d
If the area’s to be declared
Then you need pi r squared

Hope you take the opportunity to use the investigation.



Posted by on May 15, 2011 in Uncategorized


2 responses to “Hula Hoops, String, Circles and pi

  1. Guillermo Bautista

    May 20, 2011 at 11:06 pm

    Hi. Math Teachers at Play 38 is already up at

    You and your readers may want to check it out.


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