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


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


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