Beyond the answers - interesting background to this quiz

A currency named after a people

Paraguay's money, the guaraní, takes its name from the indigenous Guaraní people, whose language is still spoken by a large share of the population and holds official status alongside Spanish. The currency was introduced in 1943, replacing the peso, and the country has kept the same name for its money ever since - a rarity in a region where several neighbours have renamed or replaced their currencies during periods of inflation.

Where the equator actually crosses land

The equator passes through thirteen countries, but the Republic of the Congo is one of only a handful in Africa where it does so. In South America it runs through Ecuador, Colombia and Brazil; in Asia, through Indonesia. Turkey and Mexico, both tempting distractors, lie entirely outside the tropics, so the line never touches them.

Agatha Christie and the nursery rhyme murders

Five Little Pigs is one of Agatha Christie's later Poirot novels, published in 1942, and it borrows its structure from the nursery rhyme "This Little Piggy". The plot has Poirot reopening a sixteen-year-old poisoning case, revisiting it through the accounts of five witnesses. Christie often drew on rhymes and games for her titles, giving her mysteries an extra layer readers could try to decode.

Hafnium, boron and the logic of symbols

Hafnium takes its name from Hafnia, the Latin name for Copenhagen, where it was identified in the early 1920s; its symbol, Hf, follows the pattern of using the first letter plus a second from the name. Boron is simpler: its symbol is just B. Both sit in the periodic table, but in very different neighbourhoods - boron among the metalloids, hafnium among the transition metals.

ABBA's dream and the Karakoram

"I Have a Dream" appeared on ABBA's 1979 album Voulez-Vous and became one of their most recognisable ballads, later adapted into a hit for Westlife. Meanwhile, the Karakoram range stretches across the borders of Pakistan, India and China, home to K2 - the second-highest mountain on Earth and, by many accounts, a far harder climb than Everest.