Codes and Hidden Meaning - April 2004, All Stages

Problems

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Weekly Problem 44 - 2011

Challenge Level: Challenge Level:1

You have already used Magic Squares, now meet an Anti-Magic Square. Its properties are slightly different, but can you still solve it...

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Weekly Problem 40 - 2011

Challenge Level: Challenge Level:1

You may have seen magic squares before, but can you work out the missing numbers on this magic star?

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Weekly Problem 41 - 2011

Challenge Level: Challenge Level:1

This magic square has only been partially completed. Can you still solve it...

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Weekly Problem 42 - 2011

Challenge Level: Challenge Level:1

Four wiggles equal three woggles. Two woggles equal five waggles. Six waggles equal one wuggle. Using these, can you work out which of four values is the smallest?

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Weekly Problem 43 - 2011

Challenge Level: Challenge Level:1

The Queen of Hearts has lost her tarts! She asks each knave if he has eaten them, but how many of them are honest...

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Weekly Problem 38 - 2011

Challenge Level: Challenge Level:1

Given three concentric circles, shade in the annulus formed by the smaller two. What percentage of the larger circle is now shaded?

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Weekly Problem 36 - 2011

Challenge Level: Challenge Level:1

Imagine cutting out a circle which is just contained inside a semicircle. What fraction of the semi-circle will remain?

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What Shape and Colour?

Stage: 1 Challenge Level: Challenge Level:1

Can you fill in the empty boxes in the grid with the right shape and colour?

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Colour Wheels

Stage: 2 Challenge Level: Challenge Level:1

Imagine a wheel with different markings painted on it at regular intervals. Can you predict the colour of the 18th mark? The 100th mark?

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Symmetrical Semaphore

Stage: 2 Challenge Level: Challenge Level:1

Someone at the top of a hill sends a message in semaphore to a friend in the valley. A person in the valley behind also sees the same message. What is it?

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Ancient Runes

Stage: 2 Challenge Level: Challenge Level:1

The Vikings communicated in writing by making simple scratches on wood or stones called runes. Can you work out how their code works using the table of the alphabet?

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Hidden Meaning

Stage: 2 Challenge Level: Challenge Level:1

What is the missing symbol? Can you decode this in a similar way?

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All Seated

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Look carefully at the numbers. What do you notice? Can you make another square using the numbers 1 to 16, that displays the same properties?

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Numbered Cars

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

I was looking at the number plate of a car parked outside. Using my special code S208VBJ adds to 65. Can you crack my code and use it to find out what both of these number plates add up to?

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Semaphore Signals

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Semaphore is a way to signal the alphabet using two flags. You might want to send a message that contains more than just letters. How many other symbols could you send using this code?

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Inspector Morse

Stage: 3 Challenge Level: Challenge Level:1

You may like to read the article on Morse code before attempting this question. Morse's letter analysis was done over 150 years ago, so might there be a better allocation of symbols today?

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Brailler

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

The machine I use to produce Braille messages is faulty and one of the pins that makes a raised dot is not working. I typed a short message in Braille. Can you work out what it really says?

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Smith and Jones

Stage: 4 Challenge Level: Challenge Level:1

Mr Smith and Mr Jones are two maths teachers. By asking questions, the answers to which may be right or wrong, Mr Jones is able to find the number of the house Mr Smith lives in... Or not!

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Knapsack

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

You have worked out a secret code with a friend. Every letter in the alphabet can be represented by a binary value.

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Guesswork

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Ask a friend to choose a number between 1 and 63. By identifying which of the six cards contains the number they are thinking of it is easy to tell them what the number is.

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Readme

Stage: 5 Challenge Level: Challenge Level:1

Decipher a simple code based on the rule C=7P+17 (mod 26) where C is the code for the letter P from the alphabet. Rearrange the formula and use the inverse to decipher automatically.

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Double Time

Stage: 5 Challenge Level: Challenge Level:2 Challenge Level:2

Crack this code which depends on taking pairs of letters and using two simultaneous relations and modulus arithmetic to encode the message.

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The Public Key

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Find 180 to the power 59 (mod 391) to crack the code. To find the secret number with a calculator we work with small numbers like 59 and 391 but very big numbers are used in the real world for this.