Number 12


= 2 × 2 × 3

= 2 × 6
= 3 × 4

= 2 + 4 + 6
= 3 + 4 + 5

A dozen.

There are 12 months in a year.

12 inches in a foot and 12 old pennies in a shilling.

12 o'clock is midday or midnight. There are 12 signs of the Zodiac,

12 apostles and 12 people in a jury.

Dodecahedron (solid) Drawing of dodecahedron showing vertices

A dodecahedron has a regular pentagon on each of its 12 faces. It is one of the five Platonic solids. It has 20 vertices (or corners) and 30 edges. If you join together the centres of the faces of a dodecahedron you get an icosahedron.

Both octahedrons and cubes have 12 edges. An icosahedron has 12 vertices or corners.

The wheels of most cars are held on by 16 wheel nuts, with four for each wheel. Two important exceptions to this rule are the Citroën 2CV and the Robin Reliant which each have just 12 wheel nuts. The Citroën 2CV has three wheel nuts on each of its four wheels, while the Robin Reliant has four wheel nuts on each of its three wheels.

Number 12

Hand with finger joints numbered
On one hand you can count off the numbers from 1 to 12 by touching the joints of your fingers with your thumb. There are many good arguments for counting in twelves rather than in tens.

There are 12 ways of arranging eight queens on a chessboard so that no queen can capture any other queen (not counting rotations and reflections as being different). Can you find one of these chessboard arrangements?

Under British law, when you reach the age of 12 –

Pattern made using 12 parallelograms
12 parallelograms fit together to make this pattern. What are the internal angles in the parallelograms?

Twelfth Night or the Feast of Epiphany on January 6 marks the end of the Christmas period. It used to be a time of great merrymaking. Shakespeare's play Twelfth Night was written to be performed as part of the Twelfth Night celebrations.

A cartwheel with 12 spokes
A cartwheel with 12 spokes. What other symmetry patters occur in wheels?