Brain Teasers
The Bookworm
A bookworm eats from the first page of encyclopedia number 1 to the last page of encyclopaedia number 5. The bookworm eats in a straight line. Each encyclopedia consists of 400 pages. Each leaf is 0.01 inches thick and each cover is 0.25 inches thick. What distance does the bookworm eat through?
Answer
The bookworm nibbles his way through approximately eight inches. The first page of the first volume is the rightmost page of the first volume. The last page of the last volume is the leftmost page of the last volume. So the only part of the first volume he eats is the front cover, and the only part of the last volume he eats is the back cover.The reason the answer is not fourteen inches is that while each leaf is .01 inches thick, each leaf is two pages. So 400 pages is only two inches thick.
Finally, we say approximately eight inches because it is a matter of semantics whether the bookworm ate the first page of the first volume.
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Comments
It was not clear how the books were placed. I was thinking of them stacked on my dest with the first volume on top and the last volume on the bottom. But it is a clever problem when you have the books on a shelf in their typical order.
WHAT HOW COULD YOU COPY SOMEONE ELSES QUESTIONS?
Got me on this one, even though I had seen it before. I forgot about page placement of the 1st & last book as well as the use of leaf vs. pages. Good one.
An old one. Perhaps it should state that the encyclopaedias are in a set on a bookshelf.
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