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## 'Some Secret Codes' printed from http://nrich.maths.org/

## Some Secret Codes

Here is the alphabet:

a b c d e f g h i j k l m n o p q r s t u v w x y z

I have made a code that means we move $3$ places to the left to discover what the code stands for. But what will happen to

a b c ?

They pick up the letters left over at the end of the alphabet so that they become

You can think of the letters as if they were arranged on a wheel like this:

So can you work out what these codes stand for?

sdw - d - fdnh,

wkh - zhvw - zlqg - eorzv,

brx - duh - zrunlqj - kdug

Can you invent some messages of your own?

Can you create some different ways of coding?

### Why do this problem?

This

activity enables pupils to use some simple counting in addition and subtraction situations. It also starts pupils thinking about codes and the fun that can be had with them. Here is a

link to a short article from Jenny Murray about how she developed her interest in coding.

### Possible approach

The activity can be started off as a game in which the teacher says something about some secret ideas/thoughts they are having when looking at the alphabet. So, with the alphabet displayed as separate cards in order in front of the pupils they say they want to spell out (eg dog) but the teacher carefully goes for g r j instead of d o g.This will obviously lead to some discussion. Perhaps
other examples will be needed until the "rule" is established.

### Key questions

What do you think has happened?

What letters will you choose?

I see you've made your own code, can you tell me about it?

### Possible extension

Have a look at

this as an extension
### Possible support

Some children will need the alphabet individually in front of them.