Given a 2 by 2 by 2 skeletal cube with one route `down' the cube. How many routes are there from A to B?
Three circles have a maximum of six intersections with each other. What is the maximum number of intersections that a hundred circles could have?
A circle rolls around the outside edge of a square so that its circumference always touches the edge of the square. Can you describe the locus of the centre of the circle?
Semicircles are drawn on the sides of a rectangle ABCD. A circle passing through points ABCD carves out four crescent-shaped regions. Prove that the sum of the areas of the four crescents is equal to. . . .
Points A, B and C are the centres of three circles, each one of which touches the other two. Prove that the perimeter of the triangle ABC is equal to the diameter of the largest circle.
Find the area of the annulus in terms of the length of the chord which is tangent to the inner circle.
Which is a better fit, a square peg in a round hole or a round peg in a square hole?
What fractions of the largest circle are the two shaded regions?
How efficiently can you pack together disks?
What is the ratio of the area of a square inscribed in a semicircle to the area of the square inscribed in the entire circle?
A circle with the radius of 2.2 centimetres is drawn touching the sides of a square. What area of the square is NOT covered by the circle?
A cheap and simple toy with lots of mathematics. Can you interpret the images that are produced? Can you predict the pattern that will be produced using different wheels?
Equal circles can be arranged so that each circle touches four or six others. What percentage of the plane is covered by circles in each packing pattern? ...
Have a go at creating these images based on circles. What do you notice about the areas of the different sections?
Explain how the thirteen pieces making up the regular hexagon shown in the diagram can be re-assembled to form three smaller regular hexagons congruent to each other.
If you continue the pattern, can you predict what each of the following areas will be? Try to explain your prediction.
A floor is covered by a tessellation of equilateral triangles, each having three equal arcs inside it. What proportion of the area of the tessellation is shaded?
Investigate the different ways of cutting a perfectly circular pie into equal pieces using exactly 3 cuts. The cuts have to be along chords of the circle (which might be diameters).
Two circles are enclosed by a rectangle 12 units by x units. The distance between the centres of the two circles is x/3 units. How big is x?
Show that for any triangle it is always possible to construct 3 touching circles with centres at the vertices. Is it possible to construct touching circles centred at the vertices of any polygon?
Make five different quadrilaterals on a nine-point pegboard, without using the centre peg. Work out the angles in each quadrilateral you make. Now, what other relationships you can see?
Two intersecting circles have a common chord AB. The point C moves on the circumference of the circle C1. The straight lines CA and CB meet the circle C2 at E and F respectively. As the point C. . . .
Triangle ABC is right angled at A and semi circles are drawn on all three sides producing two 'crescents'. Show that the sum of the areas of the two crescents equals the area of triangle ABC.
Can you recreate squares and rhombuses if you are only given a side or a diagonal?
What is the same and what is different about these circle questions? What connections can you make?
A square of area 40 square cms is inscribed in a semicircle. Find the area of the square that could be inscribed in a circle of the same radius.
A circle touches the lines OA, OB and AB where OA and OB are perpendicular. Show that the diameter of the circle is equal to the perimeter of the triangle
This shape comprises four semi-circles. What is the relationship between the area of the shaded region and the area of the circle on AB as diameter?
Read all about the number pi and the mathematicians who have tried to find out its value as accurately as possible.
Identical squares of side one unit contain some circles shaded blue. In which of the four examples is the shaded area greatest?
See if you can anticipate successive 'generations' of the two animals shown here.
Medieval stonemasons used a method to construct octagons using ruler and compasses... Is the octagon regular? Proof please.
A very mathematical light - what can you see?
This article for pupils gives some examples of how circles have featured in people's lives for centuries.
An environment that enables you to investigate tessellations of regular polygons
A blue coin rolls round two yellow coins which touch. The coins are the same size. How many revolutions does the blue coin make when it rolls all the way round the yellow coins? Investigate for a. . . .
At the corner of the cube circular arcs are drawn and the area enclosed shaded. What fraction of the surface area of the cube is shaded? Try working out the answer without recourse to pencil and. . . .
M is any point on the line AB. Squares of side length AM and MB are constructed and their circumcircles intersect at P (and M). Prove that the lines AD and BE produced pass through P.
Shogi tiles can form interesting shapes and patterns... I wonder whether they fit together to make a ring?
A metal puzzle which led to some mathematical questions.
Find the ratio of the outer shaded area to the inner area for a six pointed star and an eight pointed star.
The diagram shows a regular pentagon with sides of unit length. Find all the angles in the diagram. Prove that the quadrilateral shown in red is a rhombus.
Given a square ABCD of sides 10 cm, and using the corners as centres, construct four quadrants with radius 10 cm each inside the square. The four arcs intersect at P, Q, R and S. Find the. . . .
What shape and size of drinks mat is best for flipping and catching?
Explore when it is possible to construct a circle which just touches all four sides of a quadrilateral.
Two semi-circles (each of radius 1/2) touch each other, and a semi-circle of radius 1 touches both of them. Find the radius of the circle which touches all three semi-circles.
This article gives an wonderful insight into students working on the Arclets problem that first appeared in the Sept 2002 edition of the NRICH website.
By inscribing a circle in a square and then a square in a circle find an approximation to pi. By using a hexagon, can you improve on the approximation?
A white cross is placed symmetrically in a red disc with the central square of side length sqrt 2 and the arms of the cross of length 1 unit. What is the area of the disc still showing?
Investigate the properties of quadrilaterals which can be drawn with a circle just touching each side and another circle just touching each vertex.