Introducing NRICH TWILGO
Pumpkin patch
Seega
Alquerque
Air nets
Prime magic
Like a circle in a spiral
Fruity totals
In this interactivity each fruit has a hidden value. Can you deduce what each one is worth?
Clocking off
LOGO challenge - triangles-squares-stars
Can you recreate these designs? What are the basic units? What movement is required between each unit? Some elegant use of procedures will help - variables not essential.
Charlie's delightful machine
Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?
Triangle in a trapezium
Can you find and prove the relationship between the area of a trapezium and the area of a triangle constructed within it?
Searching for mean(ing)
If you have a large supply of 3kg and 8kg weights, how many of each would you need for the average (mean) of the weights to be 6kg?
Ding dong bell
Take three from five
Caroline and James pick sets of five numbers. Charlie tries to find three that add together to make a multiple of three. Can they stop him?
Yih or Luk tsut k'i or Three Men's Morris
Some puzzles requiring no knowledge of knot theory, just a careful inspection of the patterns. A glimpse of the classification of knots and a little about prime knots, crossing numbers and knot arithmetic.
Wipeout
Can you do a little mathematical detective work to figure out which number has been wiped out?
Shaping the universe I - planet Earth
This article explores ths history of theories about the shape of our planet. It is the first in a series of articles looking at the significance of geometric shapes in the history of astronomy.
Charting success
Sprouts
Shaping the universe II - the solar system
The second in a series of articles on visualising and modelling shapes in the history of astronomy.
Charting more success
Shaping the universe III - to infinity and beyond
The third installment in our series on the shape of astronomical systems, this article explores galaxies and the universe beyond our solar system.
Marbles in a box
How many winning lines can you make in a three-dimensional version of noughts and crosses?
What is the question?
Spots and measles
99% of people who have measles have spots. Ben has spots. Do you think he has measles?
Instant insanity
Given the nets of 4 cubes with the faces coloured in 4 colours, build a tower so that on each vertical wall no colour is repeated, that is all 4 colours appear.
Hamiltonian cube
Find the length along the shortest path passing through certain points on the cube.
Funny factorisation
Using the digits 1 to 9, the number 4396 can be written as the product of two numbers. Can you find the factors?
Triangles in the middle
Nine colours
Can you use small coloured cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of each colour?
What's it worth?
There are lots of different methods to find out what the shapes are worth - how many can you find?
The bridges of Konigsberg
Investigate how networks can be used to solve a problem for the 18th Century inhabitants of Konigsberg.
Sliding puzzle
LOGO challenge - circles as animals
See if you can anticipate successive 'generations' of the two animals shown here.
Gnomon dimensions
Dicey directions
Relative time
Vector walk
Starting with two basic vector steps, which destinations can you reach on a vector walk?
Isosceles seven
Is it possible to find the angles in this rather special isosceles triangle?
The spider and the fly
A spider is sitting in the middle of one of the smallest walls in a room and a fly is resting beside the window. What is the shortest distance the spider would have to crawl to catch the fly?
Fermat's poser
Triangles within triangles
Vector journeys
Charlie likes to go for walks around a square park, while Alison likes to cut across diagonally. Can you find relationships between the vectors they walk along?
Partly circles
What is the same and what is different about these circle questions? What connections can you make?
Eulerian
Which of the five diagrams below could be drawn without taking the pen off the page and without drawing along a line already drawn?
Terminology
Given an equilateral triangle inside an isosceles triangle, can you find a relationship between the angles?
All tied up
A problem of time
Triangles within squares
Factorising with multilink
Can you find out what is special about the dimensions of rectangles you can make with squares, sticks and units?
Iff
Take a triangular number, multiply it by 8 and add 1. What is special about your answer? Can you prove it?
Pyramidal n-gon
Summing squares
Semicircular design
The diagram to the right shows a logo made from semi-circular arcs. What fraction of the logo is shaded?
Bendy quad
Four rods are hinged at their ends to form a convex quadrilateral. Investigate the different shapes that the quadrilateral can take. Be patient this problem may be slow to load.
Hypotenuse lattice points
Triangles within pentagons
Fill me up too
In Fill Me Up we invited you to sketch graphs as vessels are filled with water. Can you work out the equations of the graphs?
Tetra square
A question of scale
Use your skill and knowledge to place various scientific lengths in order of size. Can you judge the length of objects with sizes ranging from 1 Angstrom to 1 million km with no wrong attempts?
In or out?
Four arcs are drawn in a circle to create a shaded area. What fraction of the area of the circle is shaded?
Pick's theorem
Polygons drawn on square dotty paper have dots on their perimeter (p) and often internal (i) ones as well. Find a relationship between p, i and the area of the polygons.
Travelling by train
Contact
Out of the window
Star gazing
Spotting the loophole
A visualisation problem in which you search for vectors which sum to zero from a jumble of arrows. Will your eyes be quicker than algebra?
Concrete calculation
Trisected triangle
Four tiles are given. For which of them can three be placed together to form an equilateral triangle?
Corridors
Oldest and youngest
Picture story
Can you see how this picture illustrates the formula for the sum of the first six cube numbers?
Penta colour
In how many different ways can I colour the five edges of a pentagon so that no two adjacent edges are the same colour?
Making tracks
Immersion
Various solids are lowered into a beaker of water. How does the water level rise in each case?
Perception versus reality
Infographics are a powerful way of communicating statistical information. Can you come up with your own?
When the angles of a triangle don't add up to 180 degrees
Hexy-metry
A hexagon, with sides alternately a and b units in length, is inscribed in a circle. How big is the radius of the circle?
Proximity
We are given a regular icosahedron having three red vertices. Show that it has a vertex that has at least two red neighbours.