Place six toy ladybirds into the box so that there are two ladybirds in every column and every row.
Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
Choose four of the numbers from 1 to 9 to put in the squares so that the differences between joined squares are odd.
A variant on the game Alquerque
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?
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?
Can you make a train the same length as Laura's but using three differently coloured rods? Is there only one way of doing it?
NRICH December 2006 advent calendar - a new tangram for each day in the run-up to Christmas.
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?
How have the numbers been placed in this Carroll diagram? Which labels would you put on each row and column?
Take it in turns to place a domino on the grid. One to be placed horizontally and the other vertically. Can you make it impossible for your opponent to play?
Ben and his mum are planting garlic. Use the interactivity to help you find out how many cloves of garlic they might have had.
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....?
An odd version of tic tac toe
Yasmin and Zach have some bears to share. Which numbers of bears can they share so that there are none left over?
If you have only four weights, where could you place them in order to balance this equaliser?
Can you work out how to balance this equaliser? You can put more than one weight on a hook.
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?
How many trains can you make which are the same length as Matt's, using rods that are identical?
Use the interactivity to sort these numbers into sets. Can you give each set a name?
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
In your bank, you have three types of coins. The number of spots shows how much they are worth. Can you choose coins to exchange with the groups given to make the same total?
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?
Can you put the numbers 1 to 8 into the circles so that the four calculations are correct?
Place the numbers 1 to 10 in the circles so that each number is the difference between the two numbers just below it.
Twenty four games for the run-up to Christmas.
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!
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?
Move just three of the circles so that the triangle faces in the opposite direction.
Here is a chance to play a version of the classic Countdown Game.
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 card pairing game involving knowledge of simple ratio.
In this activity, the computer chooses a times table and shifts it. Can you work out the table and the shift each time?
Use the interactivity to find all the different right-angled triangles you can make by just moving one corner of the starting triangle.
How many triangles can you make using sticks that are 3cm, 4cm and 5cm long?
Use the interactivity to find out how many quarter turns the man must rotate through to look like each of the pictures.
Train game for an adult and child. Who will be the first to make the train?
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?
Choose 13 spots on the grid. Can you work out the scoring system? What is the maximum possible score?
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. . . .
A game for 2 people that everybody knows. You can play with a friend or online. If you play correctly you never lose!
How many right angles can you make using two sticks?
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?
Three beads are threaded on a circular wire and are coloured either red or blue. Can you find all four different combinations?
Use the clues to colour each square.
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?
Investigate which numbers make these lights come on. What is the smallest number you can find that lights up all the lights?
Have a go at this well-known challenge. Can you swap the frogs and toads in as few slides and jumps as possible?
How many different ways can you find to join three equilateral triangles together? Can you convince us that you have found them all?
Can you find all the different triangles on these peg boards, and find their angles?