Prime numbers

problem

Code Breaker

Age

7 to 11

Challenge level

This problem is based on a code using two different prime numbers less than 10. You'll need to multiply them together and shift the alphabet forwards by the result. Can you decipher the code?
problem

Gaxinta

Age

11 to 14

Challenge level

A number N is divisible by 10, 90, 98 and 882 but it is NOT divisible by 50 or 270 or 686 or 1764. It is also known that N is a factor of 9261000. What is N?
problem

Just Repeat

Age

11 to 14

Challenge level

Think of any three-digit number. Repeat the digits. The 6-digit number that you end up with is divisible by 91. Is this a coincidence?
problem

What's Left?

Age

5 to 7

Challenge level

Use this grid to shade the numbers in the way described. Which numbers do you have left? Do you know what they are called?
problem

Numbers as Shapes

Age

5 to 7

Challenge level

Use cubes to continue making the numbers from 7 to 20. Are they sticks, rectangles or squares?
problem

Swimming Pool Tiles

Age

7 to 11

Challenge level

This activity creates an opportunity to explore all kinds of number-related patterns.
problem

Prompt Cards

Age

7 to 11

Challenge level

These two group activities use mathematical reasoning - one is numerical, one geometric.
problem

Tom's Number

Age

7 to 11

Challenge level

Work out Tom's number from the answers he gives his friend. He will only answer 'yes' or 'no'.
problem

A Conversation Piece

Age

7 to 11

Challenge level

Take the number 6 469 693 230 and divide it by the first ten prime numbers and you'll find the most beautiful, most magic of all numbers. What is it?
problem

Penta Primes

Age

7 to 11

Challenge level

Using all ten cards from 0 to 9, rearrange them to make five prime numbers. Can you find any other ways of doing it?