Can you arrange the numbers 1 to 17 in a row so that each adjacent
pair adds up to a square number?
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?
A few extra challenges set by some young NRICH members.
Can you substitute numbers for the letters in these sums?
Problem solving is at the heart of the NRICH site. All the problems
give learners opportunities to learn, develop or use mathematical
concepts and skills. Read here for more information.
Bellringers have a special way to write down the patterns they
ring. Learn about these patterns and draw some of your own.
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?
Different combinations of the weights available allow you to make different totals. Which totals can you make?
Make a pair of cubes that can be moved to show all the days of the
month from the 1st to the 31st.
Place the numbers 1 to 8 in the circles so that no consecutive
numbers are joined by a line.
The number of plants in Mr McGregor's magic potting shed increases
overnight. He'd like to put the same number of plants in each of
his gardens, planting one garden each day. How can he do it?
How many solutions can you find to this sum? Each of the different letters stands for a different number.
In the multiplication calculation, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?
Solve this Sudoku puzzle whose clues are in the form of sums of the
numbers which should appear in diagonal opposite cells.
Use the clues to work out which cities Mohamed, Sheng, Tanya and
Bharat live in.
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?
Complete the magic square using the numbers 1 to 25 once each. Each
row, column and diagonal adds up to 65.
The NRICH team are always looking for new ways to engage teachers
and pupils in problem solving. Here we explain the thinking behind
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?
Exactly 195 digits have been used to number the pages in a book.
How many pages does the book have?
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.
This challenge extends the Plants investigation so now four or more children are involved.
Can you order pictures of the development of a frog from frogspawn
and of a bean seed growing into a plant?
Can you use the information to find out which cards I have used?
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.
What happens when you add three numbers together? Will your answer be odd or even? How do you know?
My local DIY shop calculates the price of its windows according to the area of glass and the length of frame used. Can you work out how they arrived at these prices?
Can you use your powers of logic and deduction to work out the missing information in these sporty situations?
Sweets are given out to party-goers in a particular way. Investigate the total number of sweets received by people sitting in different positions.
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?
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?
Do you notice anything about the solutions when you add and/or
subtract consecutive negative numbers?
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. . . .
Four small numbers give the clue to the contents of the four
This Sudoku, based on differences. Using the one clue number can you find the solution?
An extra constraint means this Sudoku requires you to think in
diagonals as well as horizontal and vertical lines and boxes of
Charlie and Abi 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 think?
If you take a three by three square on a 1-10 addition square and
multiply the diagonally opposite numbers together, what is the
difference between these products. Why?
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?
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 man has 5 coins in his pocket. Given the clues, can you work out
what the coins are?
A 2 by 3 rectangle contains 8 squares and a 3 by 4 rectangle
contains 20 squares. What size rectangle(s) contain(s) exactly 100
squares? Can you find them all?
A particular technique for solving Sudoku puzzles, known as "naked pair", is explained in this easy-to-read article.
Four friends must cross a bridge. How can they all cross it in just
If these elves wear a different outfit every day for as many days
as possible, how many days can their fun last?
Follow the clues to find the mystery number.
Find out what a "fault-free" rectangle is and try to make some of
Here you see the front and back views of a dodecahedron. Each
vertex has been numbered so that the numbers around each pentagonal
face add up to 65. Can you find all the missing numbers?
Four numbers on an intersection that need to be placed in the
surrounding cells. That is all you need to know to solve this