Q 01/05

How many people in a room make it more likely than not that two share a birthday, the famous birthday paradox?

A) 23

B) 57

C) 183

D) 366

Answer · why

A) 23

With 23 people the chance is 50.7%, because there are 253 different pairs who might match, not just 23 people compared with you.

Q 02/05

In the Monty Hall problem, what is the chance of winning the car by switching doors after the host reveals a goat?

A) 1/3

B) 1/2

C) 2/3

D) 3/4

Answer · why

C) 2/3

Switching wins 2/3 of the time, a result so counter-intuitive that nearly 1,000 PhDs wrote to Parade magazine insisting Marilyn vos Savant had got it ...

Q 03/05

Which Greek, whose followers reportedly could not eat beans, gives his name to the right-triangle rule a² + b² = c²?

A) Heraclitus

B) Plato

C) Socrates

D) Pythagoras

Answer · why

D) Pythagoras

Pythagoras's rule has been proved more ways than possibly any other theorem, including a proof published by future US president James Garfield.

Q 04/05

Which constant, celebrated on March 14 (also Einstein's birthday), is a circle's circumference divided by its diameter?

A) τ

B) π

C) γ

D) Ω

Answer · why

B) π

NASA's Jet Propulsion Laboratory uses π to just 15 decimal places even for interplanetary navigation, enough to size a circle 40 billion miles across ...

Q 05/05

After twenty heads in a row, what is the probability that a fair coin lands heads on the next flip?

A) 50%

B) 10%

C) 5%

D) 1%

Answer · why

A) 50%

The chance stays 50% because a coin has no memory; believing a tail is 'due' is the gambler's fallacy, also called the Monte Carlo fallacy after a 191...