Slightly pedantic, but this question was not a Fermi problem - Fermi problems are numerical approximation problems, and this one is more behavioral.
That said, I don't think they're lazy questions necessarily. However, I'm a physicist, enjoy Fermi problems (actually compulsively do the calculations when I hear a new one - a million golf balls!), and do think that order of magnitude approximations and quick unit changes are important skills to have developed.
I do think it's very lazy when they come out of a book or are riddles, because there are so many short approximations we can do at any moment. How much will the electric bill be for this office when it's August? or I just made a pot of coffee and forgot to place it back on the burner - when will it be too cold to enjoy? No accurate answer is needed or cared about, but the ability to predict important factors and come up with a list of contributing components is important.
That said, I don't think they're lazy questions necessarily. However, I'm a physicist, enjoy Fermi problems (actually compulsively do the calculations when I hear a new one - a million golf balls!), and do think that order of magnitude approximations and quick unit changes are important skills to have developed.
I do think it's very lazy when they come out of a book or are riddles, because there are so many short approximations we can do at any moment. How much will the electric bill be for this office when it's August? or I just made a pot of coffee and forgot to place it back on the burner - when will it be too cold to enjoy? No accurate answer is needed or cared about, but the ability to predict important factors and come up with a list of contributing components is important.