# Prime numbers

**52**NRICH Mathematical resources connected to

**Prime numbers**

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### Dicey Array

Watch the video of this game being played. Can you work out the rules? Which dice totals are good to get, and why?

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### Public Key Cryptography

An introduction to coding and decoding messages and the maths behind how to secretly share information.

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### Factors and Multiples Game for Two

Factors and Multiples game for an adult and child. How can you make sure you win this game?

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### Sieve of Eratosthenes

Follow this recipe for sieving numbers and see what interesting patterns emerge.

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### HCF Expression

Find out which two distinct primes less than $7$ will give the largest highest common factor of these two expressions.

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### Three Primes

Weekly Problem 6 - 2010

Can you find three primes such that their product is exactly five times their sum? Do you think you have found all possibilities?

Can you find three primes such that their product is exactly five times their sum? Do you think you have found all possibilities?

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### How much can we spend?

A country has decided to have just two different coins, 3z and 5z
coins. Which totals can be made? Is there a largest total that
cannot be made? How do you know?