Angles, Polygons and Geometrical Proof Short Problems
Outside the Nonagon
Weekly Problem 44 - 2010
Extend two of the sides of a nonagon to form an angle. How large is this acute angle?
Parallel Base
Weekly Problem 46 - 2015
The diagram shows two parallel lines and two angles. What is the value of x?
Two Exterior Triangles
Weekly Problem 35 - 2009
Two equilateral triangles have been drawn on two adjacent sides of a square. What is the angle between the triangles?
Robo-turn
Weekly Problem 16 - 2007
Can you figure out how far the robot has travelled by the time it is first facing due East?
Stellar Angles
Weekly Problem 30 - 2013
What is the angle $x$ in the star shape shown?
Square Bisection
Weekly Problem 8 - 2008
In how many ways can a square be cut in half using a single straight line cut?
Other Side
Weekly Problem 8 - 2016
Can you work out the size of the angles in a quadrilateral?
Square Within a Square Within...
What fraction of this square is shaded?
Polygon Cradle
Weekly Problem 18 - 2007
A regular pentagon together with three sides of a regular hexagon form a cradle. What is the size of one of the angles?
Isosceles Meld
Weekly Problem 9 - 2012
What is the angle QPT in this diagram?
Diagonal Division
Weekly Problem 45 - 2008
The diagram shows a regular pentagon with two of its diagonals. If all the diagonals are drawn in, into how many areas will the pentagon be divided?
Stacking Shapes
Weekly Problem 28 - 2017
The diagram on the right shows an equilateral triangle, a square and a regular pentagon. What is the sum of the interior angles of the resulting polygon?
As Long as Possible
Weekly Problem 40 - 2013
Given three sides of a quadrilateral, what is the longest that the fourth side can be?
Homely Angles
Weekly Problem 18 - 2011
Draw an equilateral triangle onto one side of a square. Can you work out one particular angle?
Angle of Overlap
Weekly Problem 26 - 2007
The diagram shows two equilateral triangles. What is the value of x?
Overlapping Beer Mats
Can you find the area of the overlap when these two beer mats are placed on top of each other?
Long Shadows
Weekly Problem 10 - 2012
If you know how long Meg's shadow is, can you work out how long the shadow is when she stands on her brother's shoulders?
Angle Please
Weekly Problem 19 - 2017
In the figure, what is the value of x?
Bishop's Paradise
Weekly Problem 37 - 2013
Which of the statements about diagonals of polygons is false?
Triangle in a Corner
The diagram shows an equilateral triangle touching two straight lines. What is the sum of the four marked angles?
Distinct Diagonals
Weekly Problem 21 - 2010
How many diagonals can you draw on this square...
Regular Vertex
A square, regular pentagon and equilateral triangle share a vertex. What is the size of the other angle?
Central Distance
Weekly Problem 1 - 2006
The diagram shows two circles enclosed in a rectangle. What is the distance between the centres of the circles?
Isometric Rhombuses
Weekly Problem 31 - 2016
The diagram shows a grid of $16$ identical equilateral triangles. How many rhombuses are there made up of two adjacent small triangles?
Half Past Two
Weekly Problem 21 - 2009
What is the angle between the two hands of a clock at 2.30?
Right-angled Request
Weekly Problem 26 - 2006
How many right angled triangles are formed by the points in this diagram?
Equilateral Pair
Weekly Problem 39 - 2016
In the diagram, VWX and XYZ are congruent equilateral triangles. What is the size of angle VWY?
Angular Reflection
Weekly Problem 28 - 2013
Two lines meet at a point. Another line through this point is reflected in both of these lines. What is the angle between the image lines?
Angle Hunt
Weekly Problem 39 - 2010
If you know three lengths and an angle in this diagram, can you find another angle by calculation?
Tent Poles
Weekly Problem 40 - 2015
In the diagram, $PT = QT = TS$ and $QS = SR$. What is the value of $x$?
Shared Vertex
Weekly Problem 38 - 2017
In the diagram, what is the value of $x$?
Perimeter in a Hexagon
Can you find the perimeter of this triangle inscribed in a hexagon?
Nonagon Angle
Weekly Problem 53 - 2012
ABCDEFGHI is a regular nine-sided polygon (called a 'nonagon' or 'enneagon'). What is the size of the angle FAE ?
Triangle in the Corner
A triangle is shaded within a regular hexagon. Can you find its area?
Adding Angles
Weekly Problem 47 - 2016
What is the sum of the six marked angles?
Diagonal Side
Can you work out the area of a square drawn on a diagonal?
Tricky Tessellations
Can you work out the fraction of the tiles that are painted black in this pattern?
Descending Angles
Given four of the angles in two triangles, can you find the smallest angle overall?
Outside the Boxes
Weekly Problem 13 - 2008
The diagram shows three squares drawn on the sides of a triangle. What is the sum of the three marked angles?
Integral Polygons
Each interior angle of a particular polygon is an obtuse angle which is a whole number of degrees. What is the greatest number of sides the polygon could have?
Radioactive Triangle
Weekly Problem 41 - 2014
Three straight lines divide an equilateral triangle into seven regions. What is the side length of the original triangle?
Triangle Split
Weekly Problem 50 - 2008
The lengths SP, SQ and SR are equal and the angle SRQ is x degrees. What is the size of angle PQR?
Fangs
Weekly Problem 7 - 2013
Three of the angles in this diagram all have size $x$. What is the value of $x$?
U in a Pentagon
Weekly Problem 18 - 2008
The diagram shows a regular pentagon. Can you work out the size of the marked angle?
Dodecagon Angles
Weekly Problem 50 - 2012
The diagram shows a regular dodecagon. What is the size of the marked angle?
Rectangle Dissection
Weekly Problem 2 - 2009
The 16 by 9 rectangle is cut as shown. Rearrange the pieces to form a square. What is the perimeter of the square?
Inscribed Hexagon
Weekly Problem 1 - 2014
The diagram shows a regular hexagon inside a rectangle. What is the sum of the four marked angles?
Six Minutes Past Eight
Weekly Problem 45 - 2007
What is the obtuse angle between the hands of a clock at 6 minutes past 8 o'clock?
Extended Parallelogram
Weekly Problem 11 - 2014
The diagram shows a parallelogram and an isosceles triangle. What is the size of angle TQR?
Right Angled Octagon
Weekly Problem 38 - 2008
A quadrilateral can have four right angles. What is the largest number of right angles an octagon can have?
Hexapentagon
Weekly Problem 53 - 2007
The diagram shows a regular pentagon and regular hexagon which overlap. What is the value of x?
Two Triangles
Prove that the angle marked $a$ is half the size of the angle marked $b$.
Square in a Triangle
Weekly Problem 33 - 2006
A square is inscribed in an isoscles right angled triangle of area $x$. What is the area of the square?
Rhombus Diagonal
Weekly Problem 19 - 2014
The diagram shows a rhombus and an isosceles triangle. Can you work out the size of the angle JFI?
Handy Angles
Weekly Problem 39 - 2008
How big is the angle between the hour hand and the minute hand of a clock at twenty to five?
Perimeter Puzzle
If four copies of this triangle are joined together to form a parallelogram, what is the largest possible perimeter of the parallelogram?
Equal Lengths
Weekly Problem 29 - 2013
An equilateral triangle is drawn inside a rhombus, both with equal side lengths. What is one of the angles of the rhombus?
Pentagon Ring
Weekly Problem 47 - 2011
Place equal, regular pentagons together to form a ring. How many pentagons will be needed?
Inner Rectangle
If the shape on the inside is a rectangle, what can you say about the shape on the outside?
Hexagon Cut Out
Weekly Problem 52 - 2012
An irregular hexagon can be made by cutting the corners off an equilateral triangle. How can an identical hexagon be made by cutting the corners off a different equilateral triangle?
Add All the Angles
Find the sum of all of the angles denoted by letters in this diagram
No Rights
Prove that the angle bisectors of a triangle can never meet at right angles.
Clock Face Angles
The time is 20:14. What is the smaller angle between the hour hand and the minute hand on an accurate analogue clock?
Trapezium Arch
Weekly Problem 27 - 2007
Ten stones form an arch. What is the size of the smallest angles of the trapezoidal stones?
Clock Angle
What is the angle between the the hands of a clock at 8:24?
Two Isosceles
Weekly Problem 37 - 2017
A quadrilateral is divided into two isosceles triangles. Can you work out the perimeter of the quadrilateral?
Parallelogram in the Middle
Weekly Problem 27 - 2013
The diagram shows a parallelogram inside a triangle. What is the value of $x$?
Heptagon Has
Weekly Problem 15 - 2012
How many of the five properties can a heptagon have?
Overbearing
A village has a pub, church and school. What is the bearing of the school from the church?
Eulerian
Weekly Problem 37 - 2014
Which of the five diagrams below could be drawn without taking the pen off the page and without drawing along a line already drawn?
Centred
Weekly Problem 13 - 2012
The diagram shows contains some equal lengths. Can you work out one of the angles?
Two Right Angles
Weekly Problem 4 - 2008
In the figure given in the problem, calculate the length of an edge.
Quarters
Weekly Problem 27 - 2014
Four congruent isosceles trapezia are placed in a square. What fraction of the square is shaded?
3-4-5 Circle
Can you find the radius of the circle inscribed inside a '3-4-5 triangle'?
Incentre Angle
Weekly Problem 1 - 2011
Use facts about the angle bisectors of this triangle to work out another internal angle.
Internal - External
Weekly Problem 12 - 2016
The diagram shows a square PQRS and two equilateral triangles RSU and PST. PQ has length 1. What is the length of TU?
Doubly Isosceles
Find the missing distance in this diagram with two isosceles triangles
Angle to Chord
Weekly Problem 23 - 2008
A triangle has been drawn inside this circle. Can you find the length of the chord it forms?
Isosceles Reduction
Weekly Problem 29 - 2010
An isosceles triangle is drawn inside another triangle. Can you work out the length of its base?
Overlapping Semicircles
Two semicircles overlap, can you find this length?
Inscribed Semicircle
Weekly Problem 43 - 2017
The diagram shows a semicircle inscribed in a right angled triangle. What is the radius of the semicircle?
Octagonal Ratio
Can you find the ratio of the area shaded in this regular octagon to the unshaded area?
Diagonal Touch
Weekly Problem 21 - 2012
Two rectangles are drawn in a rectangle. What fraction of the rectangle is shaded?
Shaded Square
Weekly Problem 41 - 2016
The diagram shows a square, with lines drawn from its centre. What is the shaded area?
Griddy Region
Weekly Problem 34 - 2008
What is the area of the region common to this triangle and square?
Garden Fence
Weekly Problem 44 - 2009
A garden has the shape of a right-angled triangle. A fence goes from the corner with the right-angle to a point on the opposite side. How long is the fence?
Overlapping Annuli
Just from the diagram, can you work out the radius of the smaller circles?
Altitude Inequalities
Weekly Problem 8 - 2010
Are you able to find triangles such that these five statements are true?
Semicircle in a Triangle
A semicircle is drawn inside a right-angled triangle. Find the distance marked on the diagram.
Circled Square
Can you find the area of this square inside a circle?