Hover your mouse over the counters to see which ones will be
removed. Click to remover them. The winner is the last one to
remove a counter. How you can make sure you win?
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?
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?
Arrange the four number cards on the grid, according to the rules,
to make a diagonal, vertical or horizontal line.
Cut four triangles from a square as shown in the picture. How many
different shapes can you make by fitting the four triangles back
Can you find all the different ways of lining up these Cuisenaire
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?
Investigate the smallest number of moves it takes to turn these
mats upside-down if you can only turn exactly three at a time.
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?
Try out the lottery that is played in a far-away land. What is the
chance of winning?
How many different triangles can you make on a circular pegboard that has nine pegs?
Place the numbers 1 to 10 in the circles so that each number is the
difference between the two numbers just below it.
Use the interactivity to find all the different right-angled
triangles you can make by just moving one corner of the starting
An environment which simulates working with Cuisenaire rods.
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....?
Have a go at this well-known challenge. Can you swap the frogs and toads in as few slides and jumps as possible?
This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?
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!
Can you put the numbers 1 to 8 into the circles so that the four
calculations are correct?
Can you put the numbers from 1 to 15 on the circles so that no
consecutive numbers lie anywhere along a continuous straight line?
Place six toy ladybirds into the box so that there are two ladybirds in every column and every row.
Can you make a cycle of pairs that add to make a square number
using all the numbers in the box below, once and once only?
Here is a chance to play a version of the classic Countdown Game.
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?
Three beads are threaded on a circular wire and are coloured either red or blue. Can you find all four different combinations?
Can you find all the different triangles on these peg boards, and
find their angles?
Choose a symbol to put into the number sentence.
Find out how we can describe the "symmetries" of this triangle and
investigate some combinations of rotating and flipping it.
If you have only four weights, where could you place them in order
to balance this equaliser?
Find out what a "fault-free" rectangle is and try to make some of
Can you complete this jigsaw of the multiplication square?
Explore the different tunes you can make with these five gourds.
What are the similarities and differences between the two tunes you
Can you see why 2 by 2 could be 5? Can you predict what 2 by 10
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?
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?
Our 2008 Advent Calendar has a 'Making Maths' activity for every
day in the run-up to Christmas.
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?
Imagine a wheel with different markings painted on it at regular
intervals. Can you predict the colour of the 18th mark? The 100th
In this activity, the computer chooses a times table and shifts it. Can you work out the table and the shift each time?
NRICH December 2006 advent calendar - a new tangram for each day in
the run-up to Christmas.
Use the interactivity to create some steady rhythms. How could you
create a rhythm which sounds the same forwards as it does
How have the numbers been placed in this Carroll diagram? Which
labels would you put on each row and column?
An interactive activity for one to experiment with a tricky tessellation
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?
Can you fit the tangram pieces into the outlines of the lobster, yacht and cyclist?
Try this interactive strategy game for 2
Can you fit the tangram pieces into the outlines of these people?
A game to be played against the computer, or in groups. Pick a 7-digit number. A random digit is generated. What must you subract to remove the digit from your number? the first to zero wins.
An interactive game for 1 person. You are given a rectangle with 50 squares on it. Roll the dice to get a percentage between 2 and 100. How many squares is this? Keep going until you get 100. . . .
Can you fit the tangram pieces into the outlines of these clocks?