Monthly Archives: June 2015

270. A whiff of cheese and exponentials

Here is an introduction to modelling exponential growth and decay … using cheese!

Exponential growth and decay (pptx)

Exponential growth and decay intro (ppt)

I used this as a starting point whilst teaching the Edexcel C3 course. You could even demonstrate with fresh and not so fresh cheese. I’m sure the staffroom or sixth form fridge will have some ‘interesting’ examples.

269. Snappy Proportion

Proportion … it comes in so many forms and different students grasp different elements at different speeds. Differentiation hell!

What about a little resource that offers up 4x8x8 variations of question ranging from simple direct to proportion to inversely proportional to the square? It’s not a new app, it’s an old app – a fortune-teller snapdragon:


Print, cut and fold (see 92. Snapdragon Fun for instructions)

  • The first decision chooses level of difficulty – students pick a number and count through the opening/shutting process.
  • The second gives the information to calculate k (eg y=kx) – the number of open/shut moves is specified.
  • The third asks you to apply your equation to a hidden number.
  • Students increase the level of challenge as they do more questions.

Download the pdf here: Proportion Snapdragon

The editable version is available here: Editable Proportion Snapdragon

You may wish to enlarge the pdf on a photocopier to make it more manageable for bigger hands.

A Blogger’s Apology

You may have noticed that the updates to MathSandpit have slowed a little. The reasons are threefold:

  1. I have a research project for the NPQSL to write up
  2. I have recently taken up the role of Head of Department for one year
  3. I’m trying to create a comprehensive index for the website

So when I have time I will add new posts, but it may not be the weekly service which you may have come to expect. In the meantime I will be tweeting older resources which you may have forgotten about.

Thank you for patience and support!