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A library has conducted a survey of its readers. The survey asked its $10,000$ readers about their reading habits and the number of books that they have borrowed from the library in $2012$. It has found that its readers claimed to have borrowed $75,000$ books in $2012$. The library has also reviewed the borrowing records of its books and found that on average a book was borrowed $5$ times. The library has $20,000$ books.

Is this survey accurate?

MITjanitor
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YahyaTyphoon
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1 Answers1

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HINT: If you add up the numbers of times each of the $20,000$ books in the library was borrowed to get the total number of borrowings, and divide that by $20,000$, you get the average of $5$ borrowings per book. That tells you that the total number of borrowings must have been ... what? Does this agree with the number of borrowings reported by the library’s readers?

Brian M. Scott
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