
Pumpkin patch

Seega

Alquerque

Introducing NRICH TWILGO

Clocking off

Fruity totals
In this interactivity each fruit has a hidden value. Can you deduce what each one is worth?

Air nets

Prime magic

Like a circle in a spiral


Charting success

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?


Charting more success

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 is the question?

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.

Spots and measles
99% of people who have measles have spots. Ben has spots. Do you think he has measles?


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.


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?

Triangles in the middle


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?

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.

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?

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.

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?

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.

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?

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.

Wipeout
Can you do a little mathematical detective work to figure out which number has been wiped out?



Slippage

The perforated cube

Rectangle rearrangement

Curvy areas
Have a go at creating these images based on circles. What do you notice about the areas of the different sections?



Mystic rose
Use the animation to help you work out how many lines are needed to draw mystic roses of different sizes.

Just opposite

Painted cube
Imagine a large cube made from small red cubes being dropped into a pot of yellow paint. How many of the small cubes will have yellow paint on their faces?

Packing boxes

Negatively triangular
How many intersections do you expect from four straight lines ? Which three lines enclose a triangle with negative co-ordinates for every point ?

Around and back

Building gnomons

Quadratic patterns
Surprising numerical patterns can be explained using algebra and diagrams...

In a box
Chris and Jo put two red and four blue ribbons in a box. They each pick a ribbon from the box without looking. Jo wins if the two ribbons are the same colour. Is the game fair?

Slick summing
Watch the video to see how Charlie works out the sum. Can you adapt his method?



Tetrahedra tester
An irregular tetrahedron is composed of four different triangles. Can such a tetrahedron be constructed where the side lengths are 4, 5, 6, 7, 8 and 9 units of length?

Newspaper sheets

Triangle midpoints
You are only given the three midpoints of the sides of a triangle. How can you construct the original triangle?

Steel cables
Some students have been working out the number of strands needed for different sizes of cable. Can you make sense of their solutions?

Pythagoras perimeters
If you know the perimeter of a right angled triangle, what can you say about the area?

Painted purple

Speed-time problems at the Olympics
Have you ever wondered what it would be like to race against Usain Bolt?

Doesn't add up
In this problem we are faced with an apparently easy area problem, but it has gone horribly wrong! What happened?

Funnel
A plastic funnel is used to pour liquids through narrow apertures. What shape funnel would use the least amount of plastic to manufacture for any specific volume ?

Summing geometric progressions
Watch the video to see how to sum the sequence. Can you adapt the method to sum other sequences?


Twelve cubed

Partly painted cube
Jo made a cube from some smaller cubes, painted some of the faces of the large cube, and then took it apart again. 45 small cubes had no paint on them at all. How many small cubes did Jo use?

Ladder and cube
A 1 metre cube has one face on the ground and one face against a wall. A 4 metre ladder leans against the wall and just touches the cube. How high is the top of the ladder above the ground?

Far horizon
An observer is on top of a lighthouse. How far from the foot of the lighthouse is the horizon that the observer can see?

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?

Which is cheaper?
When I park my car in Mathstown, there are two car parks to choose from. Can you help me to decide which one to use?

Fermat's poser

Triangles within triangles


Gnomon dimensions

Dicey directions

Speeding boats
Two boats travel up and down a lake. Can you picture where they will cross if you know how fast each boat is travelling?



All tied up

Which is bigger?
Which is bigger, n+10 or 2n+3? Can you find a good method of answering similar questions?

A problem of time

Triangles within squares



Terminology
Given an equilateral triangle inside an isosceles triangle, can you find a relationship between the angles?

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.

Track design
Where should runners start the 200m race so that they have all run the same distance by the finish?

Hypotenuse lattice points

Triangles within pentagons

Iff
Take a triangular number, multiply it by 8 and add 1. What is special about your answer? Can you prove it?

Back fitter
10 graphs of experimental data are given. Can you use a spreadsheet to find algebraic graphs which match them closely, and thus discover the formulae most likely to govern the underlying processes?