# Advent calendar 2018

## 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

arrows geometry speed probability logic 3d shapes square roots pascal's triangle complex numbers perfect numbers hexagons means factorials prime numbers shapes grids calculus scales proportion addition rectangles squares fractions christmas volume quadratics star numbers digits chess sums dates money perimeter probabilty irreducible numbers square numbers circles parabolas cube numbers polygons sequences angles books division functions colouring spheres surds factors integers cryptic crossnumbers bases coordinates triangles graphs dodecagons ellipses crosswords advent balancing chocolate cryptic clues games planes mean trigonometry triangle numbers shape chalkdust crossnumber people maths crossnumbers taxicab geometry remainders unit fractions menace symmetry coins percentages routes area clocks numbers folding tube maps averages algebra regular shapes multiples 2d shapes wordplay time rugby cards indices integration palindromes differentiation lines doubling dice number multiplication sum to infinity sport odd numbers partitions ave floors## 11 December

This puzzle is inspired by a puzzle Woody showed me at MathsJam.

Today's number is the number \(n\) such that $$\frac{216!\times215!\times214!\times...\times1!}{n!}$$ is a square number.