Pi
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119 free Pi trivia questions with answers — science & nature quiz, new questions added Oct 2026.
64 free Pi trivia questions with answers. Dive into the world of mathematics' most iconic constant with our extensive Pi trivia quiz. Featuring 119 questions spanning from basic facts to advanced mathematical concepts, this quiz challenges both math enthusiasts and curious learners. Discover how much you really know about Pi (π) and its fascinating role in science and nature.
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Q 01A famous run of six consecutive 9s in the decimal expansion of π starts at roughly which decimal place?
The 762nd
The six consecutive 9s begin at the 762nd decimal place of π, a run nicknamed the Feynman point after Richard Feynman, who joked he wanted to memorize π that far and then say 'and so on'.
Q 02Which Welsh mathematician first used the Greek letter π for the circle constant, in a 1706 book?
William Jones
William Jones printed π in his 1706 Synopsis Palmariorum Matheseos but credited its formulas to the 'ready pen' of John Machin, so some suspect Machin wrote the symbol first.
Q 03Which mathematical property of pi means its decimal expansion is infinite and non-repeating?
Irrational
Irrational numbers cannot be written as one whole number over another; every such fraction's decimal either stops or repeats, as 1/3 = 0.333... does, so π's never can.
Q 04Pi is transcendental: not the root of any non-zero polynomial with which type of coefficients?
Rational
Rational coefficients are the test: √2 solves x² − 2 = 0, so it is merely algebraic, while π solves no such equation; Cantor showed in 1874 that almost all numbers are like π.
Q 05Pi Day is celebrated annually on which date?
March 14
March 14 is written 3/14 in American date order, matching π's first three digits; the day began in 1988 as a staff party at a science museum, with fruit pies and tea.
Q 06Which Greek mathematician approximated Pi by inscribing and circumscribing polygons?
Archimedes
Archimedes trapped π between polygons drawn inside and outside a circle, doubling their sides up to 96; later calculators kept refining his method for well over a thousand years.
Q 07What are the first five digits after the decimal point of π?
14159
14159 follows the 3; the old mnemonic 'How I want a drink, alcoholic of course' hides the digits in the number of letters of each word: 3, 1, 4, 1, 5, 9.
Q 08Pi appears in which famous mathematical equation involving 'e', 'i', and '1'?
Euler's Identity
Euler's Identity, e^(iπ) + 1 = 0, is prized for economy: it ties together five fundamental constants using one addition, one multiplication and one exponentiation, and nothing else.
Q 09Roughly how many digits of π did Rajveer Meena recite for his 2015 Guinness World Record?
70,000
70,000 digits is the Guinness record: Rajveer Meena recited them blindfolded at a university in Vellore, India, in a session that lasted nearly ten hours.
Q 10A clay tablet more than 3,500 years old shows which ancient civilisation taking π as 3.125?
Babylonians
Babylonians usually made do with a plain 3 for circle sums, but this one tablet works with 3 1/8, only about half a percent below the true value.
Q 11Which Egyptian papyrus, a set of maths problems copied by the scribe Ahmes, implies π is about 3.16?
Rhind Papyrus
The Rhind Papyrus takes eight-ninths of a circle's width and multiplies it by itself to get the area; a Scottish collector, Alexander Rhind, bought the scroll in Luxor in 1858.
Q 12Which ancient text describes a round basin ten cubits across and thirty around, implying π = 3?
The Bible
The Bible's First Book of Kings gives Solomon's temple a cast 'molten sea' of those dimensions; read literally that makes π exactly 3, most likely a craftsman's round measurement, not a formula.
Q 13Which construction is impossible with compass and straightedge because Pi is transcendental?
Squaring the circle
Q 21The alternating sum π/4 = 1 − 1/3 + 1/5 − 1/7 + ... usually goes by which name?
Gregory-Leibniz Series
The Gregory-Leibniz series is lovely but nearly useless for calculation: thousands of terms are needed to get just four correct decimals of π.
Q 22In which 1960s TV series is a murderous entity foiled by ordering a computer to compute π to its last digit?
Star Trek
Star Trek's 1967 episode 'Wolf in the Fold' has Spock give the order; because π never ends, the impossible job ties up the computer that the entity had taken over.
Q 23Which famous physicist's birthday falls on Pi Day?
Albert Einstein
Squaring the circle kept tempting amateurs even after the proof that it can't be done: false 'solutions' went on arriving for generations.
Q 14Which solid has a volume of (4/3)πr³?
Sphere
A sphere's volume is (4/3)πr³, so doubling the radius multiplies the volume by eight: a 20 cm ball holds as much as eight 10 cm ones.
Q 15Pi Approximation Day honours which common fractional approximation of π?
22/7
22/7 gives the day its date, 22 July, in day-first notation; the fraction is actually a slightly closer match for π than the more familiar 3.14.
Q 16Which mathematician popularised the symbol π for the circle constant, without being the first to use it?
Leonhard Euler
Leonhard Euler took up the symbol in the 1730s, and his widely read 1748 textbook Introductio in analysin infinitorum, along with a vast correspondence, spread it across Europe.
Q 17Pi Day was first celebrated in 1988 at the Exploratorium, a science museum in which US city?
San Francisco
San Francisco's Exploratorium started it as a staff get-together; physicist Larry Shaw, later nicknamed the Prince of π, led the museum's Pi Day parades every year until his death in 2017.
Q 18Which Persian astronomer computed π to 16 decimal digits in 1424, a record for about 180 years?
Jamshid al-Kashi
Jamshid al-Kashi, working at Samarkand, computed 2π to nine sexagesimal (base-60) places in 1424, equivalent to 16 decimal digits, using a polygon of 3×2^28, more than 800 million, sides.
Q 19The Greek letter π corresponds to which letter of the Latin alphabet?
P
P is the Latin counterpart of π; the symbol was most likely picked as the initial of a Greek word for a circle's edge, 'periphery' or 'perimeter'.
Q 20Which Indian mathematician published a set of strikingly fast-converging formulae for π in 1914?
Srinivasa Ramanujan
Srinivasa Ramanujan's 1914 paper gave a series that adds about eight correct digits of π with every term; his formulae became the basis of the fastest methods used for later record computations.
Albert Einstein was born in Ulm, Germany, in 1879; Princeton, New Jersey, his home for more than twenty years, has marked the day with Einstein look-alike contests.
Q 24Chinese mathematicians in the 5th century AD approximated Pi to how many decimal places?
Seven
In the 5th century AD, Chinese mathematicians, notably Zu Chongzhi, approximated Pi to seven decimal places.
Q 25William Shanks hand-calculated 607 digits of π in 1853; at roughly which digit did his error begin?
The 528th
Shanks's error began at the 528th decimal place, so every later digit, including the 100 he added in 1873 to reach 707, was wrong; D. F. Ferguson spotted the mistake with a mechanical desk calculator in 1944.
Q 26How much longer must a rope around Earth's equator be to hover one metre above the ground all the way round?
About 6 metres
About 6 metres, or 2π times the one-metre lift, is all it takes; Earth's size drops out of the sum, so the answer would be the same for a football.
Q 27Which 18th-century polymath, whose name is on a map projection, first proved that π can't be written as a fraction?
Johann Heinrich Lambert
Johann Heinrich Lambert proved it in the 1760s using a continued fraction for the tangent function; his conic map projection of 1772 is still used for aeronautical charts.
Q 28What is the definition of the circumference of a circle?
The distance around it
The distance around it is a circle's circumference; Eratosthenes worked out Earth's in the third century BC by comparing noon shadows in two Egyptian cities.
Q 29In the cylinder volume formula V = πr²h, what does 'h' represent?
Height
In the formula for the volume of a cylinder, V = πr²h, 'h' stands for the height of the cylinder.
Q 30In 1897 an amateur mathematician nearly got which Midwestern US state's legislature to pass a bill implying π = 3.2?
Indiana
Indiana's House passed the bill without a single vote against; the state Senate then postponed it indefinitely, so the wrong value never became law.