# Puzzles

## Archive

Show me a random puzzle**Most recent collections**

#### Sunday Afternoon Maths LXVII

Coloured weightsNot Roman numerals

#### Advent calendar 2018

#### Sunday Afternoon Maths LXVI

Cryptic crossnumber #2#### Sunday Afternoon Maths LXV

Cryptic crossnumber #1Breaking Chocolate

Square and cube endings

List of all puzzles

## Tags

dates percentages hexagons partitions christmas crosswords shape averages square roots dodecagons sum to infinity geometry games surds cryptic crossnumbers ellipses rectangles squares volume proportion sums perfect numbers taxicab geometry sport addition graphs folding tube maps lines unit fractions quadratics coins odd numbers number multiples integers algebra 2d shapes digits chess time factorials routes multiplication scales speed menace symmetry circles complex numbers polygons money area fractions doubling calculus division triangle numbers irreducible numbers cards prime numbers perimeter integration numbers square numbers regular shapes arrows crossnumbers means triangles chalkdust crossnumber factors 3d shapes angles parabolas sequences trigonometry indices ave balancing grids people maths wordplay differentiation coordinates spheres dice advent books probabilty pascal's triangle colouring cryptic clues clocks logic star numbers cube numbers functions bases rugby probability chocolate mean remainders shapes floors palindromes planes## 21 December

This year, I posted instructions for making a dodecahedron and a stellated rhombicuboctahedron.

To get today's number, multiply the number of modules needed to make a dodecahedron by half the number of tube maps used to make a stellated rhombicuboctahedron.

## Folding tube maps

Back in 2012, I posted instructions for folding a tetrahedron from tube maps. When tube maps are used, the sides of the tetrahedron are not quite equal. What ratio would the rectangular maps need to be in to give a regular tetrahedron?