Suppose we define a horse's tail to be a leg. How many legs does a horse have?
This question is part of a joke, but I decided to turn it into a real question... What do you think the answer should be?!
This question is part of a joke that goes like this:
A mathematician, scientist, and engineer are each asked: "Suppose we define a horse's tail to be a leg. How many legs does a horse have?" The mathematician answers "5"; the scientist "1"; and the engineer says "But you can't do that!"
The joke is basically to ridicule engineers, as they are stereotyped to not have a great command of the concepts of hypothesizes and inferencing. But the joke includes another implicit stereotyping of the difference between mathematicians and scientists.
In the field of mathematics, new definitions and theories are usually inclusive of all the definitions and theories that preceded it. Hence, a mathematician would consider a new definition to be inclusive of previous definitions. There is actually another joke about this specific idea:
Mathematics is the art of giving the same name to different things.
Hence, the mathematician's answer is 5!
In the field of science, usually new theories replace older theories, thats why the scientist's answer assumes that the new definition abolishes the older definition. Hence the scientist answered 1!
My answer to this question is "5"... It was actually my first reaction, and also after some thought I think its most convincing. The argument is that: The question doesn't specify whether or not the conventional concept of a leg is still called a leg. First of all, we can agree that the question does not specify; Which is -after all- why the answer is debatable. But the first rule that comes to the mind is that the best answer is the one with the least problematic assumptions. As a rule of the thumb, when something is not explicitly stated to have changed, then leave it as it is. We shouldn't assume something to change when the question doesn't explicitly state that it was changed.
Update: Added an explained answer