Today is the 30th of November.

Thirty is a number closely connected to newspapers, for in the 1920s and 1930s, a "Newspaper" was underworld slang for a prison sentence of 30 days.

Thirty years is, according to the journal Nature in 1883, "the extreme limit of hippopotamian existence", which shows just how wrong scientific opinion can be. For earlier this year a hippo at Munich Zoo died at the age of 61.

Thirty is also:

The number of edges on either a dodecahedron or an icosahedron;

The number of centuries (of 100 men each) in an early Roman legion.

And in case you're wondering who coined the phrase "thirty-something", our researches indicate it was PG Wodehouse, in a description of a cricket match in a story called Prefect's Uncle (1903): "He was carting all over the shop. Made thirty something."

Competition: Word chains

Taxes-taxed-axed-axe-are-bare -bear-bead-bade-badge-budge -budget: A word chain from taxes to budget. To move from one word to the next, only one of the following is allowed:

1) changing one letter.

2) omitting one letter.

3) forming an anagram.

4) adding a letter at the beginning, end or middle.

We have three Chambers Dictionary prizes for the shortest such chains leading from "Major" to "Blair". (Words in common usage preferred.)

Entries, by 12 December, to: Pastimes, the Independent, 1 Canada Square, Canary Wharf, London E14 5DL.

9 November report:

Aristotle (realist to); Sophocles (chops lose); Archimedes (head crimes). Winners: GF Steele, Charles King, Mrs P McInnes.

16 November report:

1 Over the Eight; 2 Halves in a Game of Football; 4 Legged Friend (He'll Never Let You Down); 8 Hours in a Nine to Five Working Day; 16 Ounces in a Pound. Winners: Val McLeish, Mick Fleming, Elaine Wealleans.