12 December

These three vertices form a right angled triangle.
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.
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 

Sunday Afternoon Maths LXVII

Coloured weights
Not Roman numerals

Advent calendar 2018

Sunday Afternoon Maths LXVI

Cryptic crossnumber #2

Sunday Afternoon Maths LXV

Cryptic crossnumber #1
Breaking Chocolate
Square and cube endings

List of all puzzles


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


Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2019