Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...
The idea of this game is to add or subtract the two numbers on the dice and cover the result on the grid, trying to get a line of three. Are there some numbers that are good to aim for?
Use the clues to find out who's who in the family, to fill in the family tree and to find out which of the family members are mathematicians and which are not.
Rather than using the numbers 1-9, this sudoku uses the nine different letters used to make the words "Advent Calendar".
Each clue in this Sudoku is the product of the two numbers in adjacent cells.
Find the values of the nine letters in the sum: FOOT + BALL = GAME
An extra constraint means this Sudoku requires you to think in diagonals as well as horizontal and vertical lines and boxes of nine.
Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
Arrange 9 red cubes, 9 blue cubes and 9 yellow cubes into a large 3 by 3 cube. No row or column of cubes must contain two cubes of the same colour.
A few extra challenges set by some young NRICH members.
Imagine you have an unlimited number of four types of triangle. How many different tetrahedra can you make?
The letters of the word ABACUS have been arranged in the shape of a triangle. How many different ways can you find to read the word ABACUS from this triangular pattern?
These are the faces of Will, Lil, Bill, Phil and Jill. Use the clues to work out which name goes with each face.
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
A game for 2 people. Take turns placing a counter on the star. You win when you have completed a line of 3 in your colour.
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?
You need to find the values of the stars before you can apply normal Sudoku rules.
This tricky challenge asks you to find ways of going across rectangles, going through exactly ten squares.
Move your counters through this snake of cards and see how far you can go. Are you surprised by where you end up?
Use the interactivity to listen to the bells ringing a pattern. Now it's your turn! Play one of the bells yourself. How do you know when it is your turn to ring?
The clues for this Sudoku are the product of the numbers in adjacent squares.
A Sudoku with clues as ratios.
A Sudoku that uses transformations as supporting clues.
Given the products of diagonally opposite cells - can you complete this Sudoku?
If we had 16 light bars which digital numbers could we make? How will you know you've found them all?
Using the statements, can you work out how many of each type of rabbit there are in these pens?
A Sudoku with clues as ratios or fractions.
Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!
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?
There are seven pots of plants in a greenhouse. They have lost their labels. Perhaps you can help re-label them.
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?
Tim's class collected data about all their pets. Can you put the animal names under each column in the block graph using the information?
Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.
Make a pair of cubes that can be moved to show all the days of the month from the 1st to the 31st.
Alice and Brian are snails who live on a wall and can only travel along the cracks. Alice wants to go to see Brian. How far is the shortest route along the cracks? Is there more than one way to go?
This Sudoku puzzle can be solved with the help of small clue-numbers on the border lines between pairs of neighbouring squares of the grid.
This magic square has operations written in it, to make it into a maze. Start wherever you like, go through every cell and go out a total of 15!
What is the largest 'ribbon square' you can make? And the smallest? How many different squares can you make altogether?
In the planet system of Octa the planets are arranged in the shape of an octahedron. How many different routes could be taken to get from Planet A to Planet Zargon?
There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2 litres. Find a way to pour 9 litres of drink from one jug to another until you are left with exactly 3 litres in three of the jugs.
Can you recreate these designs? What are the basic units? What movement is required between each unit? Some elegant use of procedures will help - variables not essential.
This problem is based on the story of the Pied Piper of Hamelin. Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!
This second Sudoku article discusses "Corresponding Sudokus" which are pairs of Sudokus with terms that can be matched using a substitution rule.
First Connect Three game for an adult and child. Use the dice numbers and either addition or subtraction to get three numbers in a straight line.