manugmat123 wrote:

Keats Library purchases a number of new books, all in the category of biography; the library does not acquire any other books. With the addition of the new biographies, the biography collection of the library amounts to 37.5% of the new total number of books in the library. If prior to the purchase, only 20% of the books in Keats Library were biographies, by what percent has the number of biographies in the library increased?

A. 17.5%

B. 62.5%

C. 87.5%

D. 140%

E. 150%

Let the number of books prior to the purchase of new biographies = 100, implying that the number of biographies prior to the purchase = 20% of 100 = 20.

We can PLUG IN THE ANSWERS, which represent the percent increase in the number of biographies.

Percents on the GMAT tend to be round numbers.

Thus, the correct answer is probably D or E.

When the correct answer is plugged in:

\(\frac{(new-total-biographies)}{(new-total-books)}\) = 37.5% = \(\frac{3}{8}\).

D: 140%Here, the increase in the number of biographies = \(\frac{140}{100}\) * 20 = 28.

Thus:

\(\frac{(new-total-biographies)}{(new-total-books)}\) = \(\frac{(20+28)}{(100+28)}\)= \(\frac{48}{128}\) = \(\frac{3}{8}\).

Success!

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