Pi Day
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144 free Pi Day trivia questions with answers — science & nature quiz, new questions added Oct 2026.
50 free Pi Day trivia questions with answers. March 14 is Pi Day — the annual celebration of the mathematical constant pi (3.14159...). From ancient Babylonian clay tablets to Google Cloud supercomputers, humanity has been obsessed with this never-ending, never-repeating number for over 4,000 years. Whether you know pi to 3 digits or 300, this quiz covers everything from the basics of circles to the Chudnovsky algorithm and the Feynman point. How much do you know about the world's most famous irrational number?
30 of 144 questions with answers and explanations. Play the quiz
Q 01Which British single-board computer put its 3 Model B+ on sale on Pi Day 2018?
Raspberry Pi
Raspberry Pi began as a cheap board meant to get schoolchildren programming, and its $35 3 Model B+ went on sale on March 14, 2018.
Q 02Using pi, the volume of a cylinder with radius z and height a spells out which food?
Pizza
Pizza: a cylinder's volume is pi times the radius squared times the height, so a radius of z and a height of a give pi·z·z·a, a well-worn maths joke.
Q 03Pi is the ratio of a circle's circumference to its what?
Diameter
Diameter is the key: wrap a string once around any round object, cut it into lengths that span the middle, and you get three pieces plus a small leftover every time.
Q 04What type of number is pi?
Irrational
Irrational means no fraction ever equals pi exactly, so its decimals never end or fall into a repeating loop, and record hunters can keep computing fresh digits forever.
Q 05What is the formula for the circumference of a circle?
2πr
2πr is pi's definition rearranged: the distance around a circle is pi times the distance straight across it, and straight across is two radii, which is where the 2 comes from.
Q 06What is the formula for the area of a circle?
πr²
πr² appears when you slice a circle into thin wedges and lay them head to tail: they form a near-rectangle one radius high and half the circumference long.
Q 07Which famous physicist's birthday falls on Pi Day?
Albert Einstein
Albert Einstein was born in the city of Ulm in 1879, and the longest-running Pi Day party includes a round of 'Happy Birthday' sung in his honour.
Q 08Which space agency sets students a Pi Day Challenge built on maths from its real missions?
NASA
NASA's challenge poses the kind of problems its engineers solve with pi, such as aiming a laser signal from deep space at the spot where Earth will be when it arrives.
Q 09Which state legislature nearly passed an 1897 bill implying pi equals 3.2?
Indiana
Indiana was saved by chance: a Purdue mathematics professor happened to be at the statehouse, was shown the bill and coached the senators, who shelved it.
Q 10Which legislative body passed a 2009 resolution supporting the designation of National Pi Day?
The U.S. House
The U.S. House approved the resolution in March 2009; it urges schools to use the day to teach students about pi and draw them into mathematics.
Q 11Who organized the first large-scale Pi Day celebration in 1988?
Larry Shaw
Larry Shaw went on hosting the celebration every year until his death in 2017, and colleagues fondly called him the Prince of Pi.
Q 12At which museum was the first Pi Day celebration held?
San Francisco Exploratorium
The San Francisco Exploratorium's staff came up with the holiday at an off-site retreat in 1988, and it grew into a yearly tradition at the museum.
Q 13Which ancient Greek mathematician is famous for his method of approximating pi using polygons?
Archimedes
Archimedes inscribed and circumscribed regular polygons around a circle, doubling their sides step by step, and squeezed pi between the bounds 223/71 and 3 1/7.
Q 21Which Indian mathematician's c.1400 infinite series for pi predated Europe's by over two centuries?
Madhava
Madhava's own mathematical writings are lost; the series survives only because later scholars of his Kerala school credited it to him, long before Gregory and Leibniz found it again.
Q 22The Comte de Buffon, whose probability puzzle is a classic way to estimate pi, was chiefly famous as what?
A naturalist
A naturalist above all, Buffon spent four decades on his Histoire Naturelle, publishing 36 volumes that tried to describe the whole living world.
Q 23The ancient Greek who trapped pi between 96-sided polygons began his doubling from which shape?
A hexagon
Q 14Which Simpsons character silences a rowdy science conference by shouting that pi is exactly three?
Professor Frink
Professor Frink is struggling to quiet the hall while Lisa waits in the wings to present her discovery of why bullies pick on nerds.
Q 15How many degrees are there in π radians?
180
180 degrees is a half turn, or π radians; mathematicians favour radians because the calculus of sine and cosine only comes out clean when angles are measured that way.
Q 16Which country writes dates month-first, the format that makes 3/14 Pi Day?
United States
The United States writes dates month-first, so March 14 becomes 3/14; day-first countries such as the United Kingdom would write 14/3, which is why some mark July 22 (22/7) instead.
Q 17What does it mean that pi is a transcendental number?
Not the root of any rational polynomial
Not the root of any rational polynomial: no algebra equation with fraction coefficients has pi as a solution. Almost all numbers are like this, yet proving it for any one of them is hard.
Q 18Which ancient civilization's clay tablet, more than 3,500 years old, treats pi as 3.125?
Babylonians
Babylonians usually made do with a plain 3; this tablet, dug up near Susa in 1936, shows they also knew the sharper 3 1/8, about half a percent below the true value.
Q 19On Pi Day 2015 at 9:26:53 AM, what did the date and time together spell out?
Pi matched to 10 digits: 3.141592653
This 'Pi Instant' comes around once a century, and 2015 was billed as Super Pi Day because that year's date supplied five digits.
Q 20What is the hobby of memorizing digits of pi called, a pun on the study of language?
Piphilology
Piphilology blends 'pi' with 'philology'; devotees even write poems, called piems, in which each word's letter count gives the next digit.
A hexagon was the natural start because its perimeter is easy to work out; four doublings later, at 96 sides, he had pinned pi between 223/71 and 22/7.
Q 24Which ancient geometry challenge was proved impossible in 1882, once pi was shown to be transcendental?
Squaring the circle
Squaring the circle means building a square with exactly a circle's area using only compass and straightedge; the phrase lives on as a byword for attempting the impossible.
Q 25The "tau movement" argues that which number should replace pi as the fundamental circle constant?
2π (approximately 6.283)
2π (approximately 6.283) is one full turn in radians, so with tau a quarter turn is simply a quarter of tau; its fans celebrate on June 28, written 6/28.
Q 26What is Euler's identity, often called the most beautiful equation in mathematics?
e^(iπ) + 1 = 0
e^(iπ) + 1 = 0 came top when mathematicians rated formulas inside a brain scanner in 2014: the ones they found beautiful lit up the same emotional region as great art and music.
Q 27In 1949 John von Neumann's team spent 70 hours computing 2,037 digits of pi on which computer?
ENIAC
ENIAC was the first electronic computer ever used to compute pi, and in under three days it nearly doubled the best total people had reached in over 2,000 years of trying.
Q 28Which Indian mathematician produced pi formulas that converge extremely rapidly?
Srinivasa Ramanujan
Srinivasa Ramanujan's 1914 paper gave series for 1/π that add roughly eight correct digits per term, anticipating the fast algorithms used for record computations decades later.
Q 29Which university has often timed its admissions decision letters to arrive on Pi Day?
MIT
MIT has released its undergraduate admissions decisions on March 14 for years; in 2015 they went online at 9:26 am, that year's 'pi minute'.
Q 30Which mathematician brothers' formula, adding about 14 digits per term, carried pi past a billion digits in 1989?
Chudnovsky
The Chudnovsky brothers, David and Gregory, later built their own supercomputer in a Manhattan apartment and passed two billion digits on it.