Preferred Materials
Calculating Changes assumes that students at all levels have open access to Poly Plug and Calculators. Activities can be adapted to other resources, but to get maximum benefit from the Calculating Changes professional development programs, schools will need to invest in these resources. Some schools have made that shift by putting Poly Plug on the children's book list.


... Poly Plug
For the following reasons, activities in our Activity Banks assume the use of Poly Plug. Many activities can be adapted to other materials, but nothing else offers so much in the one resource. Besides, children simply love using them.

Poly Plug...
  • is colourful, tactile, motivating
  • is classroom savvy - noiseless, easy to pack up
  • is useful as both a structured and an unstructured aid
  • has applications across a broad range of mathematical content - pattern, counting, fractions, graphing, symmetry, problem solving
  • has even more applications when used in conjunction with other simple, readily obtainable material such as dice and cards
  • comes in a sturdy press-seal bag for easy packing up and storage
Poly Plug is also used as a support resource for the Mathematics Task Centre because many of its hands-on tasks can be converted to whole class investigations with Poly Plug. Click here to find out more about Poly Plug from that site, including how to order.


... Calculators
Calculating Changes assumes students have free access to calculators from the day they enter school. This assumption is based on research from the Calculator Aware Number (CAN) project in England, and its derivatives elsewhere.

Given this assumption we want students to use calculators which give correct answers, and the majority of four function calculators in schools don't! - see the activity Order of Operations. Simple four function machines with this Algebraic Operating System (AOS) are not common. To assist you in deciding, we have gathered the following information about appropriate machines.

Our activities assume children of all ages have open access to calculators. Some activities can work with any machine, however, if the activity involves the possibility of mixing the operations of + or - with x or ÷ the simplest (read 'cheapest') four function machines will give the wrong answer to most questions. So, use your school calculators if you wish, but beware of this limitation.

Special Notes

  1. Several Calculating Changes activities are built around showing the answer and working backwards to find the question. The two line calculators below 'give the game away' in those activities because they show both the question and the answer. This can be overcome by putting a finger (or a piece of masking tape) over the question part of the screen.
  2. Given differences in the two machines below, it may be appropriate to use the Sagitta in Years K - 2 and the Mollic in Years 3 - 6.


Mollic AMR2

Manufactured by ALEGA Skolmateriel AB, Sweden, these machines are solar powered, use an Algebraic Operation System and have a two line display. As a result the keyboard has a few more buttons, but these are not overwhelming. The calculator measures 14ˇ2cm x 7ˇ5cm and is 1ˇ1cm thick and can fit in the hand of a 5 year old. It is supported by a slide-in case. You can see more features of this calculator (in English) on the Mollic site.

During email discussions with the Manager, Göran Hjalmarsson, we have been impressed with their rapid response and sound business ethic. They can readily ship to Australia and offer the following packages:

  • 30-pack Mollic AMR2 calculators ... 340 USD including freight to Australia.
  • 60-pack Mollic AMR2 calculators ... 600 USD including freight to Australia.
  • Payment in advance by credit card.
  • Orders are placed by scanning a school purchase order and emailing directly to Göran at:
  • A response will be received within 24 hours with instructions for paying on the web using a secure credit card process.
  • The order will be packed the next day and can be expected in the school in about one week.
  • Prices were quoted at a moment in time. We suggest you contact Göran to obtain a current price.
  • Use this Currency Converter as a guide to current exchange rates.
Sagitta Basic Two-Line Calculator

Also manufactured in Sweden but available in Australia through Abacus Educational Suppliers, this simple two line calculator obeys the order of operations. It measures 12.5cm x 7.7cm x 1.4cm so fits a little more comfortably into a small hand than the Mollic above. It is supported by a slide-in case. Other features include:

  • Large digital display - two-row, clear digits, 5 and 13mm
  • Solar cell power supply
  • Durable keys made of hard plastic
  • LR54 battery for backup in poor light
  • Automatic shutoff
Price is $7.59 per unit and you can find out more at this page of the Abacus web site.



We were informed on 26th February 2015 that this machine had been discontinued due to lack of sales. You will find reference to it throughout Calculating Changes, however activities in which it is mentioned can be adapted to other calculators.

TI7 MathMate

The Texas Instruments TI 7 MathMate was brilliant, perhaps because it was designed in co-operation with leaders from the Calculator Aware Number project. However, apparently because teachers thought they were too expensive, not enough were sold and the MathMate was discontinued.

The TI 15, which has been offered as a replacement for TI 7, does have order of operations built in but:
  • it is definitely not simple
  • it costs more than the MathMate did
  • it has too many buttons
  • it requires an instruction course to learn to use its features - some of which are worthwhile - and
  • it doesn't fit comfortably into the hand of a five year old.
So, if you can find any MathMates somewhere grab them ... and if you come across any other simple four function machine with AOS built in, please let us know the details.

Calculating Changes ... is a division of ... Mathematics Centre