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The Best Card Trick?

Time for a little mathemagic! Choose any five cards from a pack and show four of them to your partner. How can they work out the fifth?

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Substitution Cipher

Find the frequency distribution for ordinary English, and use it to help you crack the code.

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Secondary Cipher Challenge Part 1

Here is the start of a six-part challenge. Can you get to the end and crack the final message?

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