Maths jokes then.
An experiment is performed involving two cats, and an inclined roof.
The two cats are very nearly identical; same gender, mass, breed, eye and fur colour.
The scientist places both cats on the apex of the roof and releases them at the same time.
One of the cats fall off the roof first.
So obviously there is some difference between the two cats.
One cat has a greater mew.
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There are 10 kinds of mathematicians. Those who can think binarily and those who can't..
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Two men are sitting in the basket of a balloon. For hours, they have been drifting through a thick layer of clouds, and they have lost orientation completely. Suddenly, the clouds part, and the two men see the top of a mountain with a man standing on it.
"Hey! Can you tell us where we are?!"
The man doesn't reply. The minutes pass as the balloon drifts past the mountain. When the balloon is about to be swallowed again by the clouds, the man on the mountain shouts: "You're in a balloon!"
"That must have been a mathematician."
"Why?"
"He thought long and thoroughly about what to say. What he eventually said was irrefutably correct. And it was of no use whatsoever..."
And as I'm a doctor, not a mathematician (dammit, Jim) a joke for doctors:
What's pink and hard?
An ECG on an orthopaedics ward.