Investigate the sum of the numbers on the top and bottom faces of a line of three dice. What do you notice?
Are these statements always true, sometimes true or never true?
In this problem we are looking at sets of parallel sticks that
cross each other. What is the least number of crossings you can
make? And the greatest?
Ben’s class were cutting up number tracks. First they cut them into twos and added up the numbers on each piece. What patterns could they see?
Only one side of a two-slice toaster is working. What is the
quickest way to toast both sides of three slices of bread?
Got It game for an adult and child. How can you play so that you know you will always win?
This challenge encourages you to explore dividing a three-digit number by a single-digit number.
For this challenge, you'll need to play Got It! Can you explain the strategy for winning this game with any target?
How many ways can you find to do up all four buttons on my coat? How about if I had five buttons? Six ...?
What happens if you join every second point on this circle? How
about every third point? Try with different steps and see if you
can predict what will happen.
This challenge, written for the Young Mathematicians' Award, invites you to explore 'centred squares'.
This activity involves rounding four-digit numbers to the nearest thousand.
Tom and Ben visited Numberland. Use the maps to work out the number of points each of their routes scores.
Choose any 3 digits and make a 6 digit number by repeating the 3
digits in the same order (e.g. 594594). Explain why whatever digits
you choose the number will always be divisible by 7, 11 and 13.
Here are two kinds of spirals for you to explore. What do you notice?
An investigation that gives you the opportunity to make and justify
Try adding together the dates of all the days in one week. Now
multiply the first date by 7 and add 21. Can you explain what
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?
Find some examples of pairs of numbers such that their sum is a
factor of their product. eg. 4 + 12 = 16 and 4 × 12 = 48 and
16 is a factor of 48.
This challenge asks you to imagine a snake coiling on itself.
Find the sum of all three-digit numbers each of whose digits is
Are these statements relating to odd and even numbers always true, sometimes true or never true?
How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?
Find a route from the outside to the inside of this square, stepping on as many tiles as possible.
This task follows on from Build it Up and takes the ideas into three dimensions!
Can you find all the ways to get 15 at the top of this triangle of numbers?
Nim-7 game for an adult and child. Who will be the one to take the last counter?
Can you dissect an equilateral triangle into 6 smaller ones? What
number of smaller equilateral triangles is it NOT possible to
dissect a larger equilateral triangle into?
This challenge focuses on finding the sum and difference of pairs of two-digit numbers.
Find the sum and difference between a pair of two-digit numbers. Now find the sum and difference between the sum and difference! What happens?
We can arrange dots in a similar way to the 5 on a dice and they
usually sit quite well into a rectangular shape. How many
altogether in this 3 by 5? What happens for other sizes?
In a Magic Square all the rows, columns and diagonals add to the 'Magic Constant'. How would you change the magic constant of this square?
Four bags contain a large number of 1s, 3s, 5s and 7s. Pick any ten numbers from the bags above so that their total is 37.
Use your addition and subtraction skills, combined with some strategic thinking, to beat your partner at this game.
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
List any 3 numbers. It is always possible to find a subset of
adjacent numbers that add up to a multiple of 3. Can you explain
why and prove it?
In how many different ways can you break up a stick of 7 interlocking cubes? Now try with a stick of 8 cubes and a stick of 6 cubes.
Place the numbers from 1 to 9 in the squares below so that the difference between joined squares is odd. How many different ways can you do this?
Caroline and James pick sets of five numbers. Charlie chooses three of them that add together to make a multiple of three. Can they stop him?
A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.
Can you see why 2 by 2 could be 5? Can you predict what 2 by 10
One block is needed to make an up-and-down staircase, with one step up and one step down. How many blocks would be needed to build an up-and-down staircase with 5 steps up and 5 steps down?
Here are some arrangements of circles. How many circles would I need to make the next size up for each? Can you create your own arrangement and investigate the number of circles it needs?
Do you notice anything about the solutions when you add and/or
subtract consecutive negative numbers?
Can you put the numbers 1-5 in the V shape so that both 'arms' have the same total?
Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?
While we were sorting some papers we found 3 strange sheets which
seemed to come from small books but there were page numbers at the
foot of each page. Did the pages come from the same book?
Use two dice to generate two numbers with one decimal place. What happens when you round these numbers to the nearest whole number?
Polygonal numbers are those that are arranged in shapes as they enlarge. Explore the polygonal numbers drawn here.
The NRICH team are always looking for new ways to engage teachers
and pupils in problem solving. Here we explain the thinking behind