Q 01/05

In the famous birthday paradox, what is the smallest group size with a better-than-even chance of a shared birthday?

A) 23

B) 57

C) 183

D) 366

Answer · why

A) 23

23 people are enough for a 50.7% chance, because they form 253 different pairs who might match, far more than the 22 comparisons any one of them makes...

Q 02/05

In the Monty Hall problem, which move wins the car two times in three?

A) Keeping the first door

B) Switching to the other door

C) Flipping a coin to decide

D) Letting the host choose

Answer · why

B) Switching to the other door

Switching to the other door wins two times in three. When Marilyn vos Savant said so in Parade magazine, thousands of readers, many signing as PhDs, w...

Q 03/05

Which Greek, whose followers were reportedly forbidden to 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 theorem even has a proof by a US president: James Garfield published one in 1876, while he was still a congressman, built around a trapez...

Q 04/05

NASA's Jet Propulsion Laboratory steers spacecraft between planets using just 15 decimal places of which constant?

A) τ

B) π

C) c

D) G

Answer · why

B) π

π to 15 decimal places is all the laboratory needs for its most exact work, because that pins the edge of a circle billions of miles across to within ...

Q 05/05

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

A) 1%

B) 5%

C) 10%

D) 50%

Answer · why

D) 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...