Use a geometric series to answer the question.
A bookshelf has 7 shelves of different widths. Each shelf is narrower than the shelf below it. The bottom three shelves
are 36 in, 31 in, 26 in. wide. If the shelf widths decrease by the
same amount from bottom to top, what is the width of
the top shelf? After you find that, what is the total shelf
space of all seven shelves?
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