12 December

There are 2600 different ways to pick three vertices of a regular 26-sided shape. Sometime the three vertices you pick form a right angled triangle.
These three vertices form a right angled triangle.
Today's number is the number of different ways to pick three vertices of a regular 26-sided shape so that the three vertices make a right angled triangle.


Show answer


In the diagram, B, A, C, D, E, F, G, H, I, J, K and L are the vertices of a regular dodecagon and B, A, M, N, O and P are the vertices of a regular hexagon.
Show that A, M and E lie on a straight line.

Show answer & extension


Show me a random puzzle
 Most recent collections 

Advent calendar 2019

Sunday Afternoon Maths LXVII

Coloured weights
Not Roman numerals

Advent calendar 2018

Sunday Afternoon Maths LXVI

Cryptic crossnumber #2

List of all puzzles


time star numbers hexagons games bases coordinates gerrymandering digits products rectangles cryptic clues square numbers dominos polygons chocolate 3d shapes indices doubling circles addition sums integration proportion menace angles dodecagons multiples people maths probability graphs quadratics ellipses calculus factors triangles rugby square roots volume grids unit fractions shapes factorials planes surds complex numbers christmas sport speed perfect numbers crossnumbers dice parabolas lines advent balancing partitions fractions folding tube maps squares area coins crossnumber mean median percentages number remainders algebra scales chalkdust crossnumber integers wordplay numbers money palindromes perimeter range probabilty clocks 2d shapes arrows geometry taxicab geometry colouring regular shapes shape pascal's triangle elections cards routes the only crossnumber dates irreducible numbers functions sequences ave tiling logic averages cryptic crossnumbers odd numbers floors digital clocks multiplication triangle numbers books means spheres symmetry cube numbers differentiation chess prime numbers sum to infinity crosswords division trigonometry


Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2020