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Primary Magazine - Issue 24: ICT in the classroom

This page has been archived. The content was correct at the time of original publication, but is no longer updated.
Created on 10 May 2010 by ncetm_administrator
Updated on 01 June 2010 by ncetm_administrator


Primary Magazine Issue 24illustration of calculator showing the word globe

ICT in the classroom

Code breaking - with calculators

The Calculator Code

calculatorThe exciting context of secret messages, codes and espionage inspires this use of ICT for Key Stage 2 pupils.

The calculator can be used to encode parts of text using calculations to spell words upside down on the screen. 0 becomes O, 1 is I, 3 is E, 4 is h, 5 is S, 6 is g, 7 is L, and 8 is B. So ‘globe’ can be made by entering 38076 and turning the calculator upside down, or by entering 19038 x 2 to achieve the same result.

This concept can be presented to children at three levels. At a basic level, children can start to break prewritten codes. This helps them to become more familiar with calculator operations and interpreting the screen, while increasing their understanding of the necessity for accurate use. Usefully, code breaking is self-checking – if the process has been carried out correctly, real words appear!

Try breaking this code with a standard school calculator and consider what calculator or mathematical skills are needed or developed to solve the puzzle:
7700 +18 hurt 1000 - 486    91 x 7 on the 15428 ÷ 2, 2 ÷ 4   √1156 had to 3 788.04 ÷ 0.01. 857² + 3 602 said “6.9606 ÷ 9” and gave him 56.63 x 100 to 6 + (3788x100).

Much more mathematical thought is required for writing these codes than breaking them. The concept could be introduced as a problem solving activity linked to finding different possibilities and sorting. First, set the children the task of recording which letters can be made on an upside-down calculator. They can work collaboratively to discover the words that can be made with those letters and will soon discover that the word needs to be entered backwards to make it correct when the calculator is turned. Encourage them to use a systematic approach to collecting and arranging lists of words that can be encoded, include opportunities for sorting using their own criteria and explaining their reasoning for doing this in their particular way.

With the set of words, start recording and sharing different calculations that could be answered to make some of them. Groups of children might decide on one particular function to apply to every word to create their code. You could restrict the function to multiplying by a number from 1 to 10 for example, if the function code is x4 then ‘hog’, which is made from 604, would become 2416 in the coded message. This gives other groups the chance to try to break the code using their knowledge of multiples of different numbers or inversions. Can the children predict any problems with using a x10 or ÷10 function code?

Depending on the children’s experience, this is an excellent opportunity to encourage the use of the calculator memory for calculations that involve more than one step, including brackets. For multi-step quick problems to solve, try displaying the calculations in a picture clue, for example, (41x25) + 67² displayed inside the outline of a snake, or (4 ÷ (101-96)) x 0.1 inside a ghost. It’s fun to observe how creative the children can be with their own calculator code picture clues! 

One of the most powerful uses of the calculator in the primary classroom is for developing an understanding of the inverse calculations or missing number problems.

Calculator code breaking can give us an exciting purpose for solving problems. Why not try this example with a spy scenario…

You have intercepted a message. You’ve just started to destroy it when you realise that it needs to be replaced in the spy’s pocket so that he does not know that you have broken the code! The decoded message reads. “Meet Bob at the Globe Theatre.”
Work out the original coded message so you can recreate it and fool the spy!

secret message

If you are feeling inspired by code breaking you should find the article The Secret World of Codes and Code Breaking interesting. The NRICH Code Breaker resource is worth exploring, it includes an on-screen interactive code breaker, ideal for collaborative problem solving. 

CPD and research
Reflect on when and how you teach calculator skills particularly considering the experiences children need to have encountered to interpret the screen accurately and to solve multi-step problems. Spend sometime watching how children use the calculator. Are their methods reliable and efficient? Do they use jottings to support their mathematics on the calculator? How do they use the calculator to support their explanation and reasoning when working collaboratively?

Calculator codes – Reinforce inverse operations and confident calculator use, and have a 4707.7 x 80 at the same time.

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