### Eight Dominoes

Using the 8 dominoes make a square where each of the columns and rows adds up to 8

### Score

There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about a total of 15 with 6 odd numbers?

### Medal Muddle

Countries from across the world competed in a sports tournament. Can you devise an efficient strategy to work out the order in which they finished?

# Inspector Morse

##### Age 11 to 14 Challenge Level:

You may like to read the article on Morse code before attempting this question.

 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 -. --- .--. --.- .-. ... - ..- ...- .-- -..- -.-- --..

Translate the following message into Morse code:

Codes and hidden meanings

If each dit (dot) takes 1 unit of time, a dah (dash) 3 units of time, the pause between letters 3 units and the pause between words 7 units, how long will it take to send this message?

Samuel Morse gave E the symbol with the shortest time value (1dit) because he thought it was the most commonly used letter. I, apparently the next most common letter, uses two dits to represent it. However, the letter analysis was done over 150 years ago and language does change and, of course, it may be entirely different in different languages.

So, might there be a better allocation of symbols today?

To tackle this question try counting the number of times each letter occurs in the article on Morse Code and suggest an alternative coding based on the frequency of each letter (this is called frequency analysis).

Would it take less time to send the message above with your code than with Morse Code? To help you there is a list of the symbols and their time in the hints.

On average would you expect your code to take less time to send a message than the international Morse Code? Could there be a more efficient coding? You might also like to look at the letter frequency graph shown in Claire Ellis' article on Codes.

Of course there is always the problem of whether the style of writing you might use to send a message is the same as that of the article. In fact, if Morse were used today I think it would most likely resemble texting.