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
A particular technique for solving Sudoku puzzles, known as "naked pair", is explained in this easy-to-read article.
Label this plum tree graph to make it totally magic!
You have been given nine weights, one of which is slightly heavier
than the rest. Can you work out which weight is heavier in just two
weighings of the balance?
Four small numbers give the clue to the contents of the four
Use the differences to find the solution to this Sudoku.
Solve this Sudoku puzzle whose clues are in the form of sums of the
numbers which should appear in diagonal opposite cells.
Can you arrange the numbers 1 to 17 in a row so that each adjacent
pair adds up to a square number?
Can you use your powers of logic and deduction to work out the missing information in these sporty situations?
This Sudoku, based on differences. Using the one clue number can you find the solution?
A pair of Sudoku puzzles that together lead to a complete solution.
Different combinations of the weights available allow you to make different totals. Which totals can you make?
Each clue number in this sudoku is the product of the two numbers in adjacent cells.
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.
Label the joints and legs of these graph theory caterpillars so that the vertex sums are all equal.
Many numbers can be expressed as the sum of two or more consecutive integers. For example, 15=7+8 and 10=1+2+3+4. Can you say which numbers can be expressed in this way?
A Sudoku with clues as ratios.
A Sudoku with clues as ratios or fractions.
Use the clues about the shaded areas to help solve this sudoku
Remember that you want someone following behind you to see where
you went. Can yo work out how these patterns were created and
Each of the main diagonals of this sudoku must contain the numbers
1 to 9 and each rectangle width the numbers 1 to 4.
Two sudokus in one. Challenge yourself to make the necessary
A Sudoku that uses transformations as supporting clues.
Rather than using the numbers 1-9, this sudoku uses the nine
different letters used to make the words "Advent Calendar".
The clues for this Sudoku are the product of the numbers in
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?
Explore this how this program produces the sequences it does. What
are you controlling when you change the values of the variables?
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. . . .
The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the $9\times9$ grid.
This is a variation of sudoku which contains a set of special clue-numbers. Each set of 4 small digits stands for the numbers in the four cells of the grid adjacent to this set.
An extra constraint means this Sudoku requires you to think in
diagonals as well as horizontal and vertical lines and boxes of
Four numbers on an intersection that need to be placed in the
surrounding cells. That is all you need to know to solve this
A package contains a set of resources designed to develop
students’ mathematical thinking. This package places a
particular emphasis on “being systematic” and is
designed to meet. . . .
Do you notice anything about the solutions when you add and/or
subtract consecutive negative numbers?
You are given the Lowest Common Multiples of sets of digits. Find
the digits and then solve the Sudoku.
Charlie and Lynne put a counter on 42. They wondered if they could
visit all the other numbers on their 1-100 board, moving the
counter using just these two operations: x2 and -5. What do you
A Latin square of order n is an array of n symbols in which each symbol occurs exactly once in each row and exactly once in each column.
You need to find the values of the stars before you can apply normal Sudoku rules.
This Sudoku combines all four arithmetic operations.
This pair of linked Sudokus matches letters with numbers and hides a seasonal greeting. Can you find it?
A Sudoku with a twist.
60 pieces and a challenge. What can you make and how many of the
pieces can you use creating skeleton polyhedra?
In this Sudoku, there are three coloured "islands" in the 9x9 grid. Within each "island" EVERY group of nine cells that form a 3x3 square must contain the numbers 1 through 9.
A few extra challenges set by some young NRICH members.
A man has 5 coins in his pocket. Given the clues, can you work out
what the coins are?
A Sudoku with clues given as sums of entries.
Four friends must cross a bridge. How can they all cross it in just
This sudoku requires you to have "double vision" - two Sudoku's for
the price of one
How many solutions can you find to this sum? Each of the different letters stands for a different number.