1. Why did 5 eat 6?

(b) Because 7, 8, 9. ("seven ate nine").

This joke has become particularly well known since it became the basis of a song by the Canadian band The Barenaked Ladies.

2. What are the 10 kinds of people in the world?

(c) Those who understand binary, and those who don't.

10 in binary is the same as 2 in decimal, and if we interpret the set-up in binary then (c) is the only punchline that makes sense.

3. What does the "B" in Benoit B Mandelbrot stand for?

(a) Benoit B Mandelbrot

Mandelbrot was the father of fractals, a term used to describe shapes that are self-similar at different scales. So, if we zoomed into the B in Benoit B Mandelbrot, then we might see that it represents a mini Benoit B Mandelbrot. If we zoomed into the mini B, we might see that it represents a micro Benoit B Mandelbrot, and so on.

4. How hard is counting in binary?

(b) It is as easy as 01, 10, 11.

01, 10, 11 is the binary equivalent of 1, 2, 3 in decimal.

5. What do you get when you cross a parrot and a banana?

(a) | parrot | x | banana | x sin θ

The joke subverts the traditional "What do you get if you cross…?" joke, because "crossing" in mathematics has a particular meaning. Crossing is an operation applied to pairs of vectors. If we think of the parrot and the banana as vectors, then the punchline correctly states that the result is the length of the banana vector multiplied by the length of the parrot vector, multiplied by the sine of the angle between them.

6. Why did the chicken cross the Möbius strip?

(a) To get to the other… er…?

A Möbius strip is a loop containing a single half twist, which means that it consists of only one surface. It has only one side. Hence, the chicken cannot get to the other side, because it does not exist.

7. What's purple and commutes?

(b) An abelian grape.

The punchline is a pun, because it sounds like "an abelian group". The elements in an abelian group are commutative, which means that changing the order of the elements for a particular mathematical operation does not affect the result (eg, 1 + 2 is the same as 2 + 1).

This is one of a whole series of jokes, such as: "What's purple, dangerous and commutes?" The answers is: "An abelian grape with a machine gun."

8. What is the world's longest song?

(a) "ℵ 1 Green Bottles Hanging on the Wall."

(c) "∞ Green Bottles Hanging on the Wall."

If you picked ∞, answer (c), then you are correct, because this symbol represents infinity. However, if you picked ℵ 1 , answer (a), you are even more correct because this represents a type of infinity that is even larger than the infinity that we typically think about! (apologies to those of you who answered (c) – our quiz algorithm can't conceive of two answers being correct)

9. What goes "Pieces of seven! Pieces of seven!"?

(b) A parroty error.

While polygon is the punchline to a joke about a dead parrot, and while polynomial is the punchline to a joke about a hungry parrot, this joke about a Long-John-Silver-type parrot refers to a mathematical test known as parity.

Parity is a term that refers to oddness or evenness, and this property can be used to test whether or not data has been corrupted. In this case, the "data" in the set-up should be "pieces of eight", but it reads as "pieces of seven", so there is clearly a parity (or "parroty") error.

10. What did Bertrand Russell say to Alfred North Whitehead?

(b) "My Gödel is killing me!"

While Freud, Goethe and Faust are all celebrated intellectuals, Kurt Gödel (pronounced "curt girdle") is the only mathematician among the multiple choice answers. Gödel, along with Russell and Whitehead, helped lay the foundations of modern mathematics. The punchline refers to a strapline used to advertise corsets in the 1970s.



Simon Singh is the author of The Simpsons and Their Mathematical Secrets