20 questions · General knowledge
Some questions come up again and again (in a quiz, in a job interview, over dinner) and it stings every time the answer will not come. Those are the ones collected here. How many letters the German alphabet has sounds like a question for first-graders until you notice that the umlauts and the ß do not count: twenty-six, with the four extra characters as additions. That Mandarin Chinese has more native speakers than any other language surprises nobody any more; that the word algebra comes from Arabic surprises many: al-dschabr means the putting together, and it reached Europe through the arithmetic books of the Middle Ages. There are the first decimal places of pi, the angles of a triangle that always add up to 180 degrees no matter how lopsided it looks, and what actually makes a number prime: divisible only by one and itself. Then come the things we use daily without being able to explain them: how many continents there are, how many planets orbit our sun, since when the euro has been in our pockets and why a leap year needs 366 days. None of this is specialist knowledge. It is the floor everything else stands on: get these cards right and you will stumble over far fewer gaps in the rest of the app.
Practise for freePurFact brings every card back right before you would forget it. That's how knowledge sticks.
Mandarin Chinese
Around a billion people speak Mandarin as their mother tongue: more than any other language.
💡 Did you know? Around a billion people speak Mandarin as their native language.
26
The basic Latin alphabet has 26 letters; German adds ä, ö, ü and ß.
💡 Did you know? With the umlauts ä, ö, ü and the ß, German adds further characters.
Arabic
„Algebra“ derives from the Arabic „al-jabr“: from the title of a medieval book of calculation.
💡 Did you know? 'Algebra' derives from the Arabic 'al-jabr'.
14159
Pi begins 3.14159… and has infinitely many decimal digits that never repeat.
💡 Did you know? Pi begins 3.14159: its digits go on forever with no pattern.
divisible only by 1 and itself
A prime number is a natural number greater than 1 divisible only by 1 and itself.
💡 Did you know? 2 is the only even prime number.
180
In any flat triangle the three interior angles always add up to exactly 180 degrees.
💡 Did you know? In a flat triangle the angles always add up to 180 degrees.
7
The rainbow is classically divided into seven colours: from red through green to violet.
💡 Did you know? The seven rainbow colours blend seamlessly into one another.
16
Since reunification in 1990 Germany has consisted of 16 federal states.
💡 Did you know? The smallest state is Bremen, the largest Bavaria.
Universal Serial Bus
„USB“ stands for Universal Serial Bus: a standardised interface for almost all devices.
💡 Did you know? USB replaced many older computer ports.
365
A normal year has 365 days; every four years a leap year adds a 29 February.
💡 Did you know? A leap year has one extra day: 29 February.
India
India overtook China in 2023 and is today the most populous country, with over 1.4 billion people.
💡 Did you know? India overtook China as the most populous country.
7
Usually seven continents are counted: Africa, Antarctica, Asia, Europe, North and South America, and Australia/Oceania.
💡 Did you know? Some models count only six, merging Europe and Asia as 'Eurasia'.
Germany
Germany lies in Central Europe; its capital is Berlin. It is the most populous country in the EU.
💡 Did you know? Black, red and gold are Germany's national colours.
2002
On 1 January 2002 euro notes and coins entered circulation, replacing the mark, franc, lira and others. As book money the euro had existed since 1999.
💡 Did you know? Euro notes deliberately show no real buildings but invented bridges and gates, so as not to favour any country.
O negative
Blood groups decide which blood is compatible: transfusing the wrong type makes it clump dangerously.
💡 Did you know? Type O-negative blood is compatible with almost any recipient.
8
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto has not counted since 2006.
💡 Did you know? Pluto did not shrink: the definition got sharper. A planet must have cleared its orbit, and in the Kuiper belt Pluto has not. It has been a dwarf planet ever since.
Because an orbit takes longer than 365 days
The extra quarter day adds up to a whole one every four years: which is why February gets a 29th day.
💡 Did you know? Precisely it is 365.2422 days, so every full century skips the leap year: unless the year divides by 400. 1900 was not a leap year, 2000 was.
north
More precisely, to the magnetic north pole, which lies a few hundred kilometres from the geographic one and slowly wanders.
💡 Did you know? Physically this is a muddle: since opposite poles attract, what sits at the geographic North Pole is in truth the Earth's magnetic SOUTH pole.
100
The Celsius scale is built on exactly that: 0 degrees freezing point, 100 degrees boiling point, both at normal air pressure.
💡 Did you know? On Mount Everest water boils at around 70 degrees: not hot enough to cook with. An egg would stay raw up there.
24
One zone corresponds to 15 degrees of longitude: 360 degrees divided by 24 hours. In practice the borders follow national boundaries, not the meridians.
💡 Did you know? Some countries step out of line: India and Iran are half an hour off, Nepal by 45 minutes. China spans five zones' worth of longitude but keeps a single time.
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