What is it: The more you take out, the more it becomes?

>>>Didn't want to add to the existing thread, and besides, this one requires a somewhat different logic. Experienced members of UT (who may have seen this few years ago) please wait a day or two before letting on the solution.
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>>>If two people dig a hole in two days, how long will it take four people to dig half a hole?
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>>I think I know the solution to this one.
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>>Reminds me of a problem in one of Asimov's books: "If one-and-a-half chickens lay one-and-a-half eggs in one-and-a-half days, how many eggs will nine chickens lay in nine days?" The super-computer to whom the question was posed answered "54", and one of the computer technicians commented, to another one, "You see, stupid?" (I translated this back from the German version I read). This was in one of the robot stories.
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>>Here is another problem: If you throw 5 heaps of stones, and 3 heaps of stones, together, how many heaps do you have?
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>>Hilmar.
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>You will have 8 heaps less than you had before throwing... :)