Place the numbers 1 to 10 in the circles so that each number is the difference between the two numbers just below it.
There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?
Have a go at this well-known challenge. Can you swap the frogs and toads in as few slides and jumps as possible?
Find out what a "fault-free" rectangle is and try to make some of your own.
Use the interactivity to find all the different right-angled triangles you can make by just moving one corner of the starting triangle.
This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?
Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
How many different triangles can you make on a circular pegboard that has nine pegs?
Can you find all the different triangles on these peg boards, and find their angles?
What do the numbers shaded in blue on this hundred square have in common? What do you notice about the pink numbers? How about the shaded numbers in the other squares?
Mr McGregor has a magic potting shed. Overnight, the number of plants in it doubles. He'd like to put the same number of plants in each of three gardens, planting one garden each day. Can he do it?
Our 2008 Advent Calendar has a 'Making Maths' activity for every day in the run-up to Christmas.
You have 4 red and 5 blue counters. How many ways can they be placed on a 3 by 3 grid so that all the rows columns and diagonals have an even number of red counters?
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?
A tetromino is made up of four squares joined edge to edge. Can this tetromino, together with 15 copies of itself, be used to cover an eight by eight chessboard?
Can you see why 2 by 2 could be 5? Can you predict what 2 by 10 will be?
NRICH December 2006 advent calendar - a new tangram for each day in the run-up to Christmas.
Is it possible to place 2 counters on the 3 by 3 grid so that there is an even number of counters in every row and every column? How about if you have 3 counters or 4 counters or....?
Can you find all the different ways of lining up these Cuisenaire rods?
Try out the lottery that is played in a far-away land. What is the chance of winning?
Cut four triangles from a square as shown in the picture. How many different shapes can you make by fitting the four triangles back together?
Can you put the numbers 1 to 8 into the circles so that the four calculations are correct?
Hover your mouse over the counters to see which ones will be removed. Click to remove them. The winner is the last one to remove a counter. How you can make sure you win?
Place six toy ladybirds into the box so that there are two ladybirds in every column and every row.
Can you put the numbers from 1 to 15 on the circles so that no consecutive numbers lie anywhere along a continuous straight line?
Can you fit the tangram pieces into the outline of this telephone?
Carry out some time trials and gather some data to help you decide on the best training regime for your rowing crew.
Can you fit the tangram pieces into the outline of Granma T?
Can you logically construct these silhouettes using the tangram pieces?
Imagine picking up a bow and some arrows and attempting to hit the target a few times. Can you work out the settings for the sight that give you the best chance of gaining a high score?
Here is a chance to play a version of the classic Countdown Game.
Can you fit the tangram pieces into the outlines of these clocks?
Try entering different sets of numbers in the number pyramids. How does the total at the top change?
Can you fit the tangram pieces into the outline of Wai Ping, Wah Ming and Chi Wing?
Start by putting one million (1 000 000) into the display of your calculator. Can you reduce this to 7 using just the 7 key and add, subtract, multiply, divide and equals as many times as you like?
Can you fit the tangram pieces into the outlines of the candle and sundial?
Can you fit the tangram pieces into the outline of Mai Ling?
This article gives you a few ideas for understanding the Got It! game and how you might find a winning strategy.
Find out how we can describe the "symmetries" of this triangle and investigate some combinations of rotating and flipping it.
Place the numbers from 1 to 9 in the squares below so that the difference between joined squares is odd. How many different ways can you do this?
Three beads are threaded on a circular wire and are coloured either red or blue. Can you find all four different combinations?
Use the interactivity to investigate what kinds of triangles can be drawn on peg boards with different numbers of pegs.
Starting with the number 180, take away 9 again and again, joining up the dots as you go. Watch out - don't join all the dots!
Explore the different tunes you can make with these five gourds. What are the similarities and differences between the two tunes you are given?
Can you locate the lost giraffe? Input coordinates to help you search and find the giraffe in the fewest guesses.
Can you fit the tangram pieces into the outline of Little Ming?
Can you make the green spot travel through the tube by moving the yellow spot? Could you draw a tube that both spots would follow?
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
What are the coordinates of the coloured dots that mark out the tangram? Try changing the position of the origin. What happens to the coordinates now?
Ahmed has some wooden planks to use for three sides of a rabbit run against the shed. What quadrilaterals would he be able to make with the planks of different lengths?