Beyond the answers - interesting background to this quiz

A plumber who became a pop culture landmark

Mario first appeared in 1981's Donkey Kong, though he was known then simply as "Jumpman." The 1985 release of Super Mario Bros. on the Nintendo Entertainment System turned him into a global icon and helped revive the home console market after the crash of 1983. His design - moustache, cap, overalls - was shaped partly by the limits of early pixel graphics, which made a recognisable silhouette more important than fine detail.

Ankara, a capital chosen deliberately

When Turkey became a republic in 1923, the capital moved from Istanbul to Ankara. The new government wanted a seat away from the old imperial centre and closer to the country's geographic heart. Istanbul remains Turkey's largest city and its economic and cultural hub, which is why it so often gets mistaken for the capital.

The war that was meant to be over by Christmas

The First World War ran from 1914 to 1918, but the fighting did not stop neatly when the calendar turned. The Armistice of 11 November 1918 ended hostilities on the Western Front, and the Treaty of Versailles followed in 1919. The dates 1939-1945 belong to the Second World War, which is why the two conflicts are easy to confuse under pressure.

Mercury's impossible temperature swing

Mercury has almost no atmosphere to trap or distribute heat, so its surface swings between roughly 430°C in sunlight and -180°C at night. That contrast is the most extreme of any planet in the solar system. Venus, by comparison, is hotter overall but far more uniform, thanks to its dense, heat-trapping atmosphere.

Roman numerals and the art of subtraction

Roman numerals normally add up - CLII is 100 + 50 + 1 + 1, or 152. But the system also uses subtraction, which is why IV means 4 and IX means 9 rather than the longer IIII or VIIII. That small rule is what keeps longer numbers like 1994 (MCMXCIV) from becoming unwieldy strings of repeated symbols.