Keats Library purchases a number of new books, all in the category of biography; the library does not acquire any other

[BTGmoderatorDC]

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%


OA D

Source: Manhattan Prep

[swerve]

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%


OA D

Source: Manhattan Prep

Before the purchase: the biography collection of the library amounted to \(20\% \; (1/5 \text{ th})\) of the total number of books. So, before the purchase, \(1\) out of \(5\) books were biographies.

After the purchase: the biography collection of the library amounted to \(37.5\%\; (3/8 \text{ th})\) of the NEW total number of books. So, after the purchase, \(3\) out of \(8\) books were biographies.