Try grouping the dominoes in the ways described. Are there any left over each time? Can you explain why?
Have a good look at these images. Can you describe what is happening? There are plenty more images like this on NRICH's Exploring Squares CD.
Can you put the numbers from 1 to 15 on the circles so that no consecutive numbers lie anywhere along a continuous straight line?
This was a problem for our birthday website. Can you use four of these pieces to form a square? How about making a square with all five pieces?
Find out why these matrices are magic. Can you work out how they were made? Can you make your own Magic Matrix?
Kaia is sure that her father has worn a particular tie twice a week in at least five of the last ten weeks, but her father disagrees. Who do you think is right?
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
Draw some isosceles triangles with an area of $9$cm$^2$ and a vertex at (20,20). If all the vertices must have whole number coordinates, how many is it possible to draw?
When number pyramids have a sequence on the bottom layer, some interesting patterns emerge...
Imagine you have an unlimited number of four types of triangle. How many different tetrahedra can you make?
Ever thought of playing three dimensional Noughts and Crosses? This problem might help you visualise what's involved.
Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.
Libby Jared helped to set up NRICH and this is one of her favourite problems. It's a problem suitable for a wide age range and best tackled practically.
Can you use small coloured cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of each colour?
Lyndon chose this as one of his favourite problems. It is accessible but needs some careful analysis of what is included and what is not. A systematic approach is really helpful.
There are many different methods to solve this geometrical problem - how many can you find?
A new problem posed by Lyndon Baker who has devised many NRICH problems over the years.
Nick Lord says "This problem encapsulates for me the best features of the NRICH collection."