This Sudoku, based on differences. Using the one clue number can you find the solution?
Can you arrange the numbers 1 to 17 in a row so that each adjacent
pair adds up to a square number?
Four friends must cross a bridge. How can they all cross it in just
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?
Follow the clues to find the mystery number.
Can you use the information to find out which cards I have used?
Use the clues to work out which cities Mohamed, Sheng, Tanya and
Bharat live in.
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?
An extra constraint means this Sudoku requires you to think in
diagonals as well as horizontal and vertical lines and boxes of
A man has 5 coins in his pocket. Given the clues, can you work out
what the coins are?
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?
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 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?
Exactly 195 digits have been used to number the pages in a book.
How many pages does the book have?
Try out the lottery that is played in a far-away land. What is the
chance of winning?
If these elves wear a different outfit every day for as many days
as possible, how many days can their fun last?
Place the numbers 1 to 8 in the circles so that no consecutive
numbers are joined by a line.
A particular technique for solving Sudoku puzzles, known as "naked pair", is explained in this easy-to-read article.
Can you order pictures of the development of a frog from frogspawn
and of a bean seed growing into a plant?
Use the differences to find the solution to this Sudoku.
Can you use your powers of logic and deduction to work out the missing information in these sporty situations?
When you throw two regular, six-faced dice you have more chance of getting one particular result than any other. What result would that be? Why is this?
Sweets are given out to party-goers in a particular way. Investigate the total number of sweets received by people sitting in different positions.
A few extra challenges set by some young NRICH members.
Solve this Sudoku puzzle whose clues are in the form of sums of the
numbers which should appear in diagonal opposite cells.
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 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?
What happens when you add three numbers together? Will your answer be odd or even? How do you know?
Rather than using the numbers 1-9, this sudoku uses the nine
different letters used to make the words "Advent Calendar".
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 small numbers give the clue to the contents of the four
Roll two red dice and a green dice. Add the two numbers on the red dice and take away the number on the green. What are all the different possibilities that could come up?
This challenging activity involves finding different ways to distribute fifteen items among four sets, when the sets must include three, four, five and six items.
This challenge extends the Plants investigation so now four or more children are involved.
Make a pair of cubes that can be moved to show all the days of the
month from the 1st to the 31st.
Bellringers have a special way to write down the patterns they
ring. Learn about these patterns and draw some of your own.
You need to find the values of the stars before you can apply normal Sudoku 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.
Look carefully at the numbers. What do you notice? Can you make
another square using the numbers 1 to 16, that displays the same
Can you help the children find the two triangles which have the
lengths of two sides numerically equal to their areas?
George and Jim want to buy a chocolate bar. George needs 2p more
and Jim need 50p more to buy it. How much is the chocolate bar?
This pair of linked Sudokus matches letters with numbers and hides a seasonal greeting. Can you find it?
Are all the possible combinations of two shapes included in this
set of 27 cards? How do you know?
A Sudoku with clues as ratios.
Tim had nine cards each with a different number from 1 to 9 on it.
How could he have put them into three piles so that the total in
each pile was 15?
Find out about Magic Squares in this article written for students. Why are they magic?!
This practical challenge invites you to investigate the different
squares you can make on a square geoboard or pegboard.
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....?
A Sudoku with a twist.