Pesky Flies

I had a great week working with the dedicated teachers in Ernabella last week. It was hot and the sticky little flies were everywhere. Fortunately, Helga, one of the teachers, gave me a present, well two actually. She gave me a very special fly net and the chance to make a problematized situation to go with it. Here is a picture of me wearing the fly net and alongside it a description about why this very special fly net has flies printed on the top of it.

Problematised situation

This is the picture of the top of a fly net. The designer was told to print 101 flies on the top of it because then the flies would think there was no room to land and so would fly away and pester other people. Now here’s the problem: the designer can’t seem to count carefully enough to check that there are actually 101 flies on the to of the net. Can you please work out how many there are and a way of proving that you counted them all, in a fast way if you can?


The designer is also wondering about how many big flies and how many little flies because he has been asked to design a new net top but with 115 flies on it and more big flies than before. Please give him some ideas but make sure it is easy to check how many flies without having to count one by one.

It’s not every day that we come across a large quantity which has been randomly organised, so this a rare real example where magnitude and counting come together so well and involve:

  • helping to bridge between trusting the count and
  • the need for unitising by making countable units.

This activity would fit in well with the ideas presented in our newest product, Early Place Value. Send any work samples to Johnny at. We would love to include a few work samples on the site and talk about what they show us.

Enjoy … and thanks, Helga! That fly net was a real life-saver.