How many solutions can you find to this sum? Each of the different letters stands for a different number.
Move your counters through this snake of cards and see how far you can go. Are you surprised by where you end up?
Can you find six numbers to go in the Daisy from which you can make all the numbers from 1 to a number bigger than 25?
Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.
Each clue in this Sudoku is the product of the two numbers in adjacent cells.
Can you arrange the digits 1, 1, 2, 2, 3 and 3 to make a Number Sandwich?
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?
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.
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?
Imagine you have an unlimited number of four types of triangle. How many different tetrahedra can you make?
A few extra challenges set by some young NRICH members.
The clues for this Sudoku are the product of the numbers in adjacent squares.
Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.
My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?
How many different symmetrical shapes can you make by shading triangles or squares?
If you are given the mean, median and mode of five positive whole numbers, can you find the numbers?
Rather than using the numbers 1-9, this sudoku uses the nine different letters used to make the words "Advent Calendar".
Use the differences to find the solution to this Sudoku.
Draw some isosceles triangles with an area of $9$cm$^2$ and a vertex at (20,20). If all the vertices must have whole number coordinates, how many is it possible to draw?
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.
This task encourages you to investigate the number of edging pieces and panes in different sized windows.
A Sudoku with clues given as sums of entries.
A Sudoku that uses transformations as supporting clues.
Two sudokus in one. Challenge yourself to make the necessary connections.
Find all the ways of placing the numbers 1 to 9 on a W shape, with 3 numbers on each leg, so that each set of 3 numbers has the same total.
Place the 16 different combinations of cup/saucer in this 4 by 4 arrangement so that no row or column contains more than one cup or saucer of the same colour.
A Sudoku with clues as ratios.
Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?
There is a long tradition of creating mazes throughout history and across the world. This article gives details of mazes you can visit and those that you can tackle on paper.
A Sudoku with clues as ratios or fractions.
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?
Given the products of diagonally opposite cells - can you complete this Sudoku?
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 puzzle can be solved with the help of small clue-numbers which are either placed on the border lines between selected pairs of neighbouring squares of the grid or placed after slash marks on. . . .
Can you coach your rowing eight to win?
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?
You need to find the values of the stars before you can apply normal Sudoku rules.
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...
Four numbers on an intersection that need to be placed in the surrounding cells. That is all you need to know to solve this sudoku.
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
This pair of linked Sudokus matches letters with numbers and hides a seasonal greeting. Can you find it?
An extra constraint means this Sudoku requires you to think in diagonals as well as horizontal and vertical lines and boxes of nine.
Bellringers have a special way to write down the patterns they ring. Learn about these patterns and draw some of your own.
Given the products of adjacent cells, can you complete this Sudoku?
Different combinations of the weights available allow you to make different totals. Which totals can you make?
A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly £100 if the prices are £10 for adults, 50p for pensioners and 10p for children.
Whenever a monkey has peaches, he always keeps a fraction of them each day, gives the rest away, and then eats one. How long could he make his peaches last for?
A Sudoku with clues as ratios.
A Sudoku with a twist.
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.