The red ring is inside the blue ring in this picture. Can you rearrange the rings in different ways? Perhaps you can overlap them or put one outside another?

Using the cards 2, 4, 6, 8, +, - and =, what number statements can you make?

A 2-Digit number is squared. When this 2-digit number is reversed and squared, the difference between the squares is also a square. What is the 2-digit number?

With one cut a piece of card 16 cm by 9 cm can be made into two pieces which can be rearranged to form a square 12 cm by 12 cm. Explain how this can be done.

We asked what was the most interesting fact that you can find out about the number 2009. See the solutions that were submitted.

This article for teachers suggests ideas for activities built around 10 and 2010.

Weekly Problem 10 - 2014

What is the sum of the first $2011$ digits when $20 \div 11$ is written as a decimal?

What is the difference between the sum of the first 2014 odd numbers and the sum of the first 2014 even numbers?

Resources used by the NRICH Secondary team in their sessions at the 2017 ATM Easter and MA Stirling conferences.

Twenty-four tasks for the run-up to Christmas.

Resources used by Alison and Charlie in their workshop at BCME 2018.

Twenty-four tasks for the run-up to Christmas.

Twenty four tasks to count down to Christmas.

It is 225 minutes until midnight. What time is it on a 24-hour digital clock?

Can you find ways of joining cubes together so that 28 faces are visible?

Two circles of equal size intersect and the centre of each circle is on the circumference of the other. What is the area of the intersection? Now imagine that the diagram represents two spheres of. . . .

A holding page for the resources and links from the second stemNRICH TI day for 2012-13.

Yatir from Israel wrote this article on numbers that can be written as $ 2^n-n $ where n is a positive integer.