my favourite mathematical joke
A biologist, physicist and mathematician are travelling by train in Scotland. Out of the window, they see a black sheep.
"Look, the sheep in Scotland are black," says the biologist.
"No, we can conclude only that some sheep in Scotland are black," says the physicist.
The mathematician says: "No, we know only that there is at least one sheep in Scotland, at least one side of which is black!"
my other favourite mathematical joke
A biologist, physicist and mathematician are in a café, watching a house across the street. They see three people enter the house, and a while later four people leave the house.
The physicist says: "I thought the house was empty at the start. There must have been a measurement error."
The biologist says: "Why? They could have reproduced in the meantime."
The mathematician says: "Both of you are wrong. If one person enters the house, it will be empty again."