A jigsaw where pieces only go together if the fractions are equivalent.

Here is a chance to create some attractive images by rotating shapes through multiples of 90 degrees, or 30 degrees, or 72 degrees or...

I start with a red, a blue, a green and a yellow marble. I can trade any of my marbles for three others, one of each colour. Can I end up with exactly two marbles of each colour?

Make a clinometer and use it to help you estimate the heights of tall objects.

I start with a red, a green and a blue marble. I can trade any of my marbles for two others, one of each colour. Can I end up with five more blue marbles than red after a number of such trades?

Make an equilateral triangle by folding paper and use it to make patterns of your own.

Delight your friends with this cunning trick! Can you explain how it works?

Arrange your fences to make the largest rectangular space you can. Try with four fences, then five, then six etc.

How can you make an angle of 60 degrees by folding a sheet of paper twice?

Make your own double-sided magic square. But can you complete both sides once you've made the pieces?

These are pictures of the sea defences at New Brighton. Can you work out what a basic shape might be in both images of the sea wall and work out a way they might fit together?

What do these two triangles have in common? How are they related?

If these balls are put on a line with each ball touching the one in front and the one behind, which arrangement makes the shortest line of balls?

What shapes should Elly cut out to make a witch's hat? How can she make a taller hat?

These practical challenges are all about making a 'tray' and covering it with paper.

Move your counters through this snake of cards and see how far you can go. Are you surprised by where you end up?

What is the largest number of circles we can fit into the frame without them overlapping? How do you know? What will happen if you try the other shapes?

An activity making various patterns with 2 x 1 rectangular tiles.

Learn how to draw circles using Logo. Wait a minute! Are they really circles? If not what are they?

Are all the possible combinations of two shapes included in this set of 27 cards? How do you know?

What happens to the area of a square if you double the length of the sides? Try the same thing with rectangles, diamonds and other shapes. How do the four smaller ones fit into the larger one?

Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.

Can you predict when you'll be clapping and when you'll be clicking if you start this rhythm? How about when a friend begins a new rhythm at the same time?

Can you fit the tangram pieces into the outline of Granma T?

Here's a simple way to make a Tangram without any measuring or ruling lines.

Can you make the birds from the egg tangram?

Starting with four different triangles, imagine you have an unlimited number of each type. How many different tetrahedra can you make? Convince us you have found them all.

You could use just coloured pencils and paper to create this design, but it will be more eye-catching if you can get hold of hammer, nails and string.

Ideas for practical ways of representing data such as Venn and Carroll diagrams.

More Logo for beginners. Learn to calculate exterior angles and draw regular polygons using procedures and variables.

Generate three random numbers to determine the side lengths of a triangle. What triangles can you draw?

Can Jo make a gym bag for her trainers from the piece of fabric she has?

Use the lines on this figure to show how the square can be divided into 2 halves, 3 thirds, 6 sixths and 9 ninths.

Where can you put the mirror across the square so that you can still "see" the whole square? How many different positions are possible?

Arrange your fences to make the largest rectangular space you can. Try with four fences, then five, then six etc.

NRICH December 2006 advent calendar - a new tangram for each day in the run-up to Christmas.

The triangle ABC is equilateral. The arc AB has centre C, the arc BC has centre A and the arc CA has centre B. Explain how and why this shape can roll along between two parallel tracks.

Here is a solitaire type environment for you to experiment with. Which targets can you reach?

These squares have been made from Cuisenaire rods. Can you describe the pattern? What would the next square look like?

Let's say you can only use two different lengths - 2 units and 4 units. Using just these 2 lengths as the edges how many different cuboids can you make?

Can you recreate this Indian screen pattern? Can you make up similar patterns of your own?

Can you fit the tangram pieces into the outline of this junk?

How many models can you find which obey these rules?

This practical problem challenges you to create shapes and patterns with two different types of triangle. You could even try overlapping them.

Looking at the picture of this Jomista Mat, can you decribe what you see? Why not try and make one yourself?

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?

Can you make the most extraordinary, the most amazing, the most unusual patterns/designs from these triangles which are made in a special way?

Using different numbers of sticks, how many different triangles are you able to make? Can you make any rules about the numbers of sticks that make the most triangles?