Pi Math
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93 free Pi Math trivia questions with answers — science & nature quiz, new questions added Oct 2026.
20 free Pi Math trivia questions with answers. Pi Math trivia lives in two places on BrainPickle. This page is the shorter set; the main quiz is Pi trivia, with our deepest question pool on the topic and a source behind every answer.
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Q 01Which ratio in a circle defines the mathematical constant π?
Circumference to diameter
Circumference to diameter is the ratio π, and it is the same for every circle: anything round, from a coin to a Ferris wheel, is a little over three times as far around as it is across.
Q 02Which Welsh mathematician first used the symbol π for the circle constant, in a 1706 textbook?
William Jones
William Jones introduced π in his 1706 Synopsis Palmariorum Matheseos, a beginners' book built from his teaching notes, but the symbol only caught on after Leonhard Euler took it up in the 1730s.
Q 03Which ancient Greek approximated pi using inscribed and circumscribed polygons?
Archimedes
Archimedes trapped π between two bounds by drawing hexagons inside and outside a circle, then doubling their sides four times until he was working with 96-sided polygons.
Q 04Which book describes a great round basin as ten cubits across and thirty cubits around?
The Bible
The Bible's First Book of Kings gives these round figures for the great cast-metal 'Sea' of Solomon's Temple, figures that work out to a π of exactly 3.
Q 05In The Simpsons, who silences a rowdy science conference by shouting that pi is exactly three?
Professor Frink
Professor Frink shouts it because nothing else will quieten the hall: the claim that π has a neat, exact value is so wrong that the scientists gasp and the noise stops.
Q 06Which US state's lower house unanimously passed a bill in 1897 that would have legislated a wrong value of π?
Indiana
Indiana's House first sent the bill to its Committee on Canals, then passed it 67–0; a Purdue professor who was visiting to lobby for funding coached the senators, and they shelved it.
Q 07Whose name usually goes with π/4 = 1 − 1/3 + 1/5 − ..., an infinite series also found by Madhava?
Leibniz
Leibniz found the series in 1673, two years after James Gregory and more than two centuries after Madhava's school in India; it converges so slowly that 500,000 terms give only five correct decimals.
Q 08Which 18th-century French naturalist posed the needle-dropping probability problem that can be used to estimate π?
Comte de Buffon
Comte de Buffon asked how often a needle dropped on a ruled floor lands across a line; for a needle as long as the gap between lines the chance is 2/π, so counting crossings gives an estimate of π.
Q 09The Chudnovsky brothers computed billions of digits of π on a supercomputer they built in their apartment in which US city?
New York
New York: the Soviet-born brothers assembled the machine from mail-order parts in Gregory Chudnovsky's Manhattan apartment, and it passed two billion digits in the early 1990s.
Q 10Which famous named equation, e^(iπ) + 1 = 0, links the five constants e, i, π, 1 and 0?
Euler's identity
Euler's identity is Euler's formula e^(ix) = cos x + i sin x evaluated at x = π: since cos π = −1 and sin π = 0, e^(iπ) equals −1, and adding 1 gives 0.
Q 11In 1991 Dave Boll noticed the digits of π emerging from iteration counts at the 'neck' of which famous fractal?
The Mandelbrot set
The Mandelbrot set hides π at its neck: test points 0.1, 0.01 and 0.001 above the pinch at −0.75 take 33, 315 and 3,143 steps to escape, creeping toward the digits of π.
Q 12A clay tablet from 1900–1600 BCE implying π = 25/8 comes from which ancient civilization?
Babylonian
Babylonian scribes' 25/8 is 3.125, within one percent of π and a clear step up from the round value of 3 that other ancient texts settled for.
Q 13Which Chinese mathematician gave the fraction 355/113 for π around 480 AD, unmatched for centuries?
Zu Chongzhi
Q 21Which physicist was born on 14 March 1879, a date now celebrated as Pi Day?
Albert Einstein
Albert Einstein was born in Ulm on 14 March 1879; Pi Day's founders only noticed the coincidence a few years in, then added a celebration of his life to the festivities.
Q 22Which famous physicist died on Pi Day, 14 March 2018?
Stephen Hawking
Stephen Hawking was told at 21 that motor neurone disease left him about two years to live; he lived another 55, dying at 76 on Pi Day.
Q 23In 2019 UNESCO designated 14 March as the International Day of what?
Mathematics
Mathematics got its international day on 14 March because many countries already marked the date as Pi Day; the first edition, in 2020, took the theme 'Mathematics is Everywhere'.
Zu Chongzhi pinned π between 3.1415926 and 3.1415927, but the Zhui Shu, the book in which he explained his method, was later lost, so nobody knows exactly how he did it.
Q 14Which mathematician first proved in the 1760s that π is irrational, using a continued fraction for the tangent function?
Johann Heinrich Lambert
Johann Heinrich Lambert showed that the tangent of every rational number except 0 is irrational; since the tangent of π/4 is exactly 1, π/4 cannot be rational, and neither can π.
Q 15Where were Ludolph van Ceulen's 35 decimals of π, his life's work, engraved?
On his tombstone
On his tombstone in Leiden: the original stone was later lost and a replica was unveiled in 2000, and German speakers long called π the Ludolphine number after him.
Q 16What is the formula for the area of a circle?
πr²
The area of a circle is πr²; a disk of radius 1 has area π ≈ 3.14159, and doubling the radius quadruples the area, since the formula scales with r².
Q 17What is the formula for the volume of a sphere?
(4/3)πr³
The volume of a sphere is (4/3)πr³, exactly two-thirds of the cylinder that just encloses it, and the very same two-thirds ratio turns out to hold for the two shapes' total surface areas.
Q 18Which inverse trig function has Taylor series x − x³/3 + x⁵/5 − …?
arctan(x)
arctan(x) has this series, and since arctan(1) = π/4, setting x = 1 turns it into a formula for π; feeding it small fractions instead converges far faster, which is how π was computed for over two centuries.
Q 19What is the run of six consecutive 9s starting at the 762nd decimal place of pi called?
The Feynman Point
The Feynman Point is named after physicist Richard Feynman, who is said to have wanted to memorise π up to those six 9s so that he could recite them and finish 'and so on', as if π were rational.
Q 20Pi Day began in 1988 at which San Francisco science museum?
The Exploratorium
The Exploratorium held the first Pi Day with fruit pies and a march around one of its circular spaces, the idea of staff physicist Larry Shaw, nicknamed the Prince of Pi.
Q 24Which fraction is celebrated on Pi Approximation Day?
22/7
22/7 is 22 July written day first; at about 3.1429 it is actually closer to π than the 3.14 that Pi Day itself celebrates.
Q 25The constant τ, championed as a replacement for π, equals what?
2π
τ equals 2π, so one full turn is exactly τ radians and a quarter turn is simply a quarter of τ, which is the case its fans make against π.
Q 26If a rope around Earth's equator were lengthened by 6.3 metres, how high could the whole rope be lifted?
About 100 centimetres
About 100 centimetres, a full metre: the gain in height depends only on the extra length, not on the size of the ball, so the same 6.3 metres would lift a rope around a tennis ball just as high.
Q 27Which university has often released its admissions decisions on Pi Day, a nod to its maths-loving applicants?
MIT
MIT has often timed its decisions for Pi Day, and in 2020 it posted them at 1:59 pm so that the date and time together spelled out the first six digits of π.
Q 28On 'Super Pi Day' 2015, which clock time completed the first ten digits of pi?
9:26:53
9:26:53 follows the date 3/14/15 to spell 3.141592653, the first ten digits of π, a line-up that month-first calendars see only once a century.
Q 29Asteroid 314159 is named after which maths communicator known for Pi Day challenges?
Matt Parker
Matt Parker, the Stand-up Maths YouTuber, is known for Pi Day stunts in which he calculates π by hand; asteroid 314159 Mattparker, named in 2024, carries the constant's first six digits in its number.
Q 30The 314th day of a common year, an unofficial second Pi Day, falls in which month?
November
November: the first ten months of a common year hold 304 days, so day 314 is 10 November; in leap years the date slips to 9 November.