Mr McGregor has a magic potting shed. Overnight, the number of
plants in it doubles. He'd like to put the same number of plants in
each of three gardens, planting one garden each day. Can he do it?
Starting with the number 180, take away 9 again and again, joining up the dots as you go. Watch out - don't join all the dots!
If you have only four weights, where could you place them in order
to balance this equaliser?
How have the numbers been placed in this Carroll diagram? Which labels would you put on each row and column?
Place six toy ladybirds into the box so that there are two ladybirds in every column and every row.
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?
Have a go at this well-known challenge. Can you swap the frogs and toads in as few slides and jumps as possible?
Can you complete this jigsaw of the multiplication square?
Try to stop your opponent from being able to split the piles of counters into unequal numbers. Can you find a strategy?
What do the numbers shaded in blue on this hundred square have in common? What do you notice about the pink numbers? How about the shaded numbers in the other squares?
Start by putting one million (1 000 000) into the display of your
calculator. Can you reduce this to 7 using just the 7 key and add,
subtract, multiply, divide and equals as many times as you like?
Choose a symbol to put into the number sentence.
Place the numbers 1 to 10 in the circles so that each number is the
difference between the two numbers just below it.
This problem is based on a code using two different prime numbers
less than 10. You'll need to multiply them together and shift the
alphabet forwards by the result. Can you decipher the code?
A game for 2 people that everybody knows. You can play with a
friend or online. If you play correctly you never lose!
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
Here is a chance to play a version of the classic Countdown Game.
Can you make a cycle of pairs that add to make a square number
using all the numbers in the box below, once and once only?
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....?
Investigate the smallest number of moves it takes to turn these
mats upside-down if you can only turn exactly three at a time.
Can you see why 2 by 2 could be 5? Can you predict what 2 by 10
Can you put the numbers 1 to 8 into the circles so that the four
calculations are correct?
A generic circular pegboard resource.
A train building game for 2 players.
Use the interactivities to complete these Venn diagrams.
Choose 13 spots on the grid. Can you work out the scoring system? What is the maximum possible score?
Using angular.js to bind inputs to outputs
Cut four triangles from a square as shown in the picture. How many
different shapes can you make by fitting the four triangles back
Can you find all the different ways of lining up these Cuisenaire
An environment which simulates working with Cuisenaire rods.
Imagine a wheel with different markings painted on it at regular
intervals. Can you predict the colour of the 18th mark? The 100th
An interactive game to be played on your own or with friends.
Imagine you are having a party. Each person takes it in turns to
stand behind the chair where they will get the most chocolate.
A card pairing game involving knowledge of simple ratio.
This article gives you a few ideas for understanding the Got It! game and how you might find a winning strategy.
Use the interactivity to find all the different right-angled triangles you can make by just moving one corner of the starting triangle.
What are the coordinates of the coloured dots that mark out the
tangram? Try changing the position of the origin. What happens to
the coordinates now?
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?
You have 4 red and 5 blue counters. How many ways can they be
placed on a 3 by 3 grid so that all the rows columns and diagonals
have an even number of red counters?
Can you put the numbers from 1 to 15 on the circles so that no
consecutive numbers lie anywhere along a continuous straight line?
Try out the lottery that is played in a far-away land. What is the
chance of winning?
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?
Can you make the green spot travel through the tube by moving the
yellow spot? Could you draw a tube that both spots would follow?
The idea of this game is to add or subtract the two numbers on the dice and cover the result on the grid, trying to get a line of three. Are there some numbers that are good to aim for?
This was a problem for our birthday website. Can you use four of these pieces to form a square? How about making a square with all five pieces?
A game for 2 people that can be played on line or with pens and paper. Combine your knowledege of coordinates with your skills of strategic thinking.
Work out the fractions to match the cards with the same amount of
An interactive game for 1 person. You are given a rectangle with 50 squares on it. Roll the dice to get a percentage between 2 and 100. How many squares is this? Keep going until you get 100. . . .
Ahmed has some wooden planks to use for three sides of a rabbit run
against the shed. What quadrilaterals would he be able to make with
the planks of different lengths?
NRICH December 2006 advent calendar - a new tangram for each day in
the run-up to Christmas.
There are nine teddies in Teddy Town - three red, three blue and three yellow. There are also nine houses, three of each colour. Can you put them on the map of Teddy Town according to the rules?