Prime numbers

There are 53 NRICH Mathematical resources connected to Prime numbers
Coins
problem

Coins poster

Age
11 to 14
Challenge level
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A man has 5 coins in his pocket. Given the clues, can you work out what the coins are?

Xavi's T-shirt
problem

Xavi's T-shirt

Age
7 to 16
Challenge level
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How much can you read into a t-shirt?

Dicey Array
game
Favourite

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?

Public Key Cryptography
article

Public key cryptography

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

Prime counter

Age
16 to 18
Challenge level
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A short challenge concerning prime numbers.
Sieve of Eratosthenes
problem

Sieve of Eratosthenes

Age
11 to 14
Challenge level
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Follow this recipe for sieving numbers and see what interesting patterns emerge.

Number Families
problem

Number families

Age
11 to 14
Challenge level
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How many different number families can you find?
HCF Expression
problem

HCF expression

Age
11 to 14
Challenge level
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Find out which two distinct primes less than $7$ will give the largest highest common factor of these two expressions.

Three Primes
problem

Three primes

Age
14 to 16
Challenge level
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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?