Solve this Sudoku puzzle whose clues are in the form of sums of the
numbers which should appear in diagonal opposite cells.
A Sudoku with a twist.
This Sudoku, based on differences. Using the one clue number can you find the solution?
Exactly 195 digits have been used to number the pages in a book.
How many pages does the book have?
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. . . .
A Sudoku with clues as ratios.
Seven friends went to a fun fair with lots of scary rides. They
decided to pair up for rides until each friend had ridden once with
each of the others. What was the total number rides?
Four numbers on an intersection that need to be placed in the
surrounding cells. That is all you need to know to solve this
An extra constraint means this Sudoku requires you to think in
diagonals as well as horizontal and vertical lines and boxes of
A Sudoku with clues given as sums of entries.
A particular technique for solving Sudoku puzzles, known as "naked pair", is explained in this easy-to-read article.
In a square in which the houses are evenly spaced, numbers 3 and 10
are opposite each other. What is the smallest and what is the
largest possible number of houses in the square?
Two sudokus in one. Challenge yourself to make the necessary
Use the clues to work out which cities Mohamed, Sheng, Tanya and
Bharat live in.
Four small numbers give the clue to the contents of the four
Make a pair of cubes that can be moved to show all the days of the
month from the 1st to the 31st.
A few extra challenges set by some young NRICH members.
A Sudoku that uses transformations as supporting clues.
A Sudoku with clues as ratios or fractions.
Place the numbers 1 to 8 in the circles so that no consecutive
numbers are joined by a line.
This second Sudoku article discusses "Corresponding Sudokus" which are pairs of Sudokus with terms that can be matched using a substitution rule.
I was in my car when I noticed a line of four cars on the lane next
to me with number plates starting and ending with J, K, L and M.
What order were they in?
This article for teachers describes several games, found on the
site, all of which have a related structure that can be used to
develop the skills of strategic planning.
Use the differences to find the solution to this Sudoku.
This pair of linked Sudokus matches letters with numbers and hides a seasonal greeting. Can you find it?
A magician took a suit of thirteen cards and held them in his hand
face down. Every card he revealed had the same value as the one he
had just finished spelling. How did this work?
Rather than using the numbers 1-9, this sudoku uses the nine
different letters used to make the words "Advent Calendar".
If these elves wear a different outfit every day for as many days
as possible, how many days can their fun last?
Can you use the information to find out which cards I have used?
This sudoku requires you to have "double vision" - two Sudoku's for
the price of one
Can you use your powers of logic and deduction to work out the missing information in these sporty situations?
Can you order pictures of the development of a frog from frogspawn
and of a bean seed growing into a plant?
Can you find which shapes you need to put into the grid to make the
totals at the end of each row and the bottom of each column?
Sweets are given out to party-goers in a particular way. Investigate the total number of sweets received by people sitting in different positions.
How many triangles can you make on the 3 by 3 pegboard?
Systematically explore the range of symmetric designs that can be
created by shading parts of the motif below. Use normal square
lattice paper to record your results.
Can you put plus signs in so this is true? 1 2 3 4 5 6 7 8 9 = 99
How many ways can you do it?
How can you arrange the 5 cubes so that you need the smallest number of Brush Loads of paint to cover them? Try with other numbers of cubes as well.
This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?
Ram divided 15 pennies among four small bags. He could then pay any sum of money from 1p to 15p without opening any bag. How many pennies did Ram put in each bag?
Arrange the four number cards on the grid, according to the rules,
to make a diagonal, vertical or horizontal line.
What is the date in February 2002 where the 8 digits are
palindromic if the date is written in the British way?
What happens when you add three numbers together? Will your answer be odd or even? How do you know?
The Vikings communicated in writing by making simple scratches on
wood or stones called runes. Can you work out how their code works
using the table of the alphabet?
In how many ways can you stack these rods, following the rules?
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 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.