Pi Math
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97 free Pi Math trivia questions with answers — science & nature quiz, new questions added Aug 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 01What is the mathematical constant Pi (π) defined as?
The ratio of a circle's circumference to its diameter.
Pi (π) is a fundamental mathematical constant representing the ratio of any circle's circumference to its diameter, a value that remains constant regardless of the circle's size.
Q 02Which mathematician was the first to use the Greek letter π on its own to denote the circle constant?
William Jones
William Jones, a Welsh mathematician, introduced the symbol in his 1706 Synopsis Palmariorum Matheseos, but it only caught on after Leonhard Euler adopted it in the 1730s and 1740s.
Q 03Which ancient Greek approximated pi using inscribed and circumscribed polygons?
Archimedes
Archimedes started from hexagons and doubled the sides four times to reach 96, and his upper bound of 3 1/7 is the origin of the schoolroom approximation 22/7.
Q 04On what date is Pi Day celebrated annually?
March 14th
Pi Day is March 14th, written 3/14 in US date order to match 3.14; San Francisco's Exploratorium held the first celebration in 1988, with staff marching around a circular space and eating fruit pie.
Q 05What are the first five digits of Pi (π) after the decimal point?
14159
The first five decimals of π are 14159, so π ≈ 3.14159; the distractors come from other constants, e = 2.71828 and the golden ratio φ = 1.61803.
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 passed Bill 246 by 67–0 in 1897; Purdue professor C. A. Waldo then briefed senators on its errors, the Senate postponed it indefinitely, and it never became law.
Q 07The series π/4 = 1 − 1/3 + 1/5 − ..., found by Madhava and Gregory, is usually named after whom?
Leibniz
Leibniz found the series in 1673, two years after James Gregory, though Madhava in India had it roughly three centuries earlier; it converges so slowly that 500,000 terms give only five correct decimals.
Q 08Which probability experiment drops needles onto a lined surface to estimate pi?
Buffon's Needle problem
Buffon's Needle problem, posed by Georges-Louis Leclerc, Comte de Buffon, in 1777, links the chance that a dropped needle crosses a line to π; Mario Lazzarini's 1901 trial hit 355/113 suspiciously well.
Q 09Which brothers' algorithm is famed for its efficiency in calculating billions of digits of pi?
Chudnovsky algorithm
The Chudnovsky algorithm is a rapidly converging algorithm used for calculating Pi to a very high number of decimal places, often employed in world-record computations.
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, where cos π = −1 and sin π = 0; a 1990 readers' poll voted it the most beautiful theorem in mathematics.
Q 11The Rhind Papyrus suggests an approximation of Pi using which formula?
(16/9)^2
The papyrus's rule for a circle's area, in effect (16/9)² ≈ 3.16, is within one percent of the true value, and the same 256/81 ratio also shows up in its problem for the volume of a cylindrical granary.
Q 12A clay tablet from 1900–1600 BCE implying π = 25/8 comes from which ancient civilization?
Babylonian
The Babylonian tablet states the ratio of a regular hexagon's perimeter to its circumscribed circle as 24/25, so 3/π = 0.96 and π ≈ 3.125, within one percent of the true value.
Q 13Which Chinese mathematician gave the fraction 355/113 for π around 480 AD, unbeaten for 800 years?
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; Princeton, where he lived for over twenty years, pairs its Pi Day events with an annual Einstein look-alike contest.
Q 22Which famous physicist died on Pi Day, 14 March 2018?
Stephen Hawking
The coincidence was widely noted: Hawking died on Einstein's birthday, and 14 March is also Pi Day.
Q 23In 2019 UNESCO designated 14 March as the International Day of what?
Mathematics
The first International Day of Mathematics was marked on 14 March 2020, right as the pandemic shut most in-person events.
Zu Chongzhi worked Liu Hui's polygon algorithm out to 12,288 sides, bounding π between 3.1415926 and 3.1415927; his 355/113 is accurate to six decimals and no fraction with a smaller denominator does better.
Q 14Which mathematician first rigorously proved Pi irrational, using a continued fraction for tan(x)?
Johann Heinrich Lambert
Johann Heinrich Lambert proved Pi irrational using the continued fraction expansion of tan(x); he presented the result to the Berlin Academy in 1761 and it appeared in print in 1768.
Q 15Which Dutch mathematician's 35 decimals of π were engraved on his Leiden tombstone?
Ludolph van Ceulen
Ludolph van Ceulen spent much of his life on the polygon method, publishing 20 decimals in 1596 and reaching 35 before his death in 1610; German texts 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; Archimedes derived it around 225 BCE by showing a sphere fills two-thirds of its enclosing cylinder, a result he had carved on his tomb.
Q 18Which inverse trig function has Taylor series x − x³/3 + x⁵/5 − …?
arctan(x)
Because arctan(1) = π/4, plugging x = 1 into x − x³/3 + x⁵/5 − ... gives the series. Using arctan values at smaller arguments (Machin's formula) converges far faster and was how π was computed for two centuries.
Q 19What is the run of six consecutive 9s starting at the 762nd decimal place of pi called?
The Feynman Point
The name comes from a story that Richard Feynman wanted to memorize π up to that point so he could recite it, hit the six 9s, and say 'and so on' — though it is unclear he ever said it, and the line appears in print from Douglas Hofstadter in 1985.
Q 20Who founded Pi Day in 1988 while working at San Francisco's Exploratorium?
Larry Shaw
Larry Shaw, nicknamed the 'Prince of Pi', dreamed up Pi Day at an Exploratorium staff retreat; the first celebration in 1988 had staff and visitors march around a circular space and eat fruit pies.
Q 24Which fraction is celebrated on Pi Approximation Day?
22/7
22/7, the day/month form of 22 July, is accurate to two decimal places and was Archimedes' upper bound for π.
Q 25The constant τ, championed as a replacement for π, equals what?
2π
τ equals 2π, the ratio of a circle's circumference to its radius rather than its diameter; one full turn is τ radians, and celebrants joke about eating 'twice the pie'.
Q 26Who published The Tau Manifesto in 2010, arguing τ should replace π?
Michael Hartl
Bob Palais had argued in 2001 that π is 'wrong', proposing a three-legged π symbol; Hartl's manifesto gave the idea its name and its day.
Q 27MIT posts admissions decisions on Pi Day at 6:28 pm, a moment it calls what?
Tau Time
In 2020 MIT instead released decisions at 1:59 pm, making the first six digits of pi with the date.
Q 28On 'Super Pi Day' 2015, which clock time completed the first ten digits of pi?
9:26:53
3/14/15 9:26:53 reads as 3.141592653; the instant within that second was dubbed 'Pi Instant'.
Q 29Asteroid 314159 is named after which maths communicator known for Pi Day challenges?
Matt Parker
Matt Parker, the Stand-up Maths YouTuber, posts a Pi Day video each year estimating π by some absurd method; minor planet 314159 Mattparker carries the constant's first six digits in its number.
Q 30In a common year, the 314th day, an unofficial pi date, is which date?
10 November
10 November is the 314th day of a common year: the first ten months hold 304 days and ten more reach 314, echoing 3.14; in leap years the honour shifts to 9 November.