The books on a bookshelf are either hardcover or paperback. Sixty percent

[BTGModeratorVI]

The books on a bookshelf are either hardcover or paperback. Sixty percent of the books are paperback and half of the hardcover books are fiction. If 40% of the paperback books are fiction, what percent of the books are nonfiction?

(A) 30
(B) 40
(C) 44
(D) 56
(E) 60

Answer: D
Source: Manhattan prep

[Brent@GMATPrepNow]

The books on a bookshelf are either hardcover or paperback. Sixty percent of the books are paperback and half of the hardcover books are fiction. If 40% of the paperback books are fiction, what percent of the books are nonfiction?

(A) 30
(B) 40
(C) 44
(D) 56
(E) 60

Answer: D
Source: Manhattan prep

Time for the Double Matrix Method!
This technique can be used for most questions featuring a population in which each member has two characteristics associated with it (aka overlapping sets questions)..

Here, we have a population of books, and the two characteristics are:
- hardcover or paperback
- fiction or nonfiction

From the given information, the diagram looks like this:


Once we fill in the empty boxes, we got the following:


At this point we can see that 56 of the 100 books are nonfiction.

56/100 = 56%

Answer: D
This question type is VERY COMMON on the GMAT, so be sure to master the technique.

To learn more about the Double Matrix Method, watch this video: https://www.gmatprepnow.com/module/gmat- ... ems?id=919

Once you’re familiar with this technique, you can attempt these additional practice questions:

Easy Problem Solving questions
- https://www.beatthegmat.com/finance-majo ... 67425.html

Medium Problem Solving questions
- https://www.gmatprepnow.com/module/gmat- ... /video/920
- https://www.beatthegmat.com/posted-speed ... 72374.html
- https://www.beatthegmat.com/motel-t271938.html
- https://www.beatthegmat.com/of-the-appli ... 70255.html
- https://www.beatthegmat.com/opening-nigh ... 64869.html
- https://www.beatthegmat.com/at-least-100 ... 74669.html
- https://www.beatthegmat.com/prblem-solving-t279424.html

Difficult Problem Solving questions
- https://www.gmatprepnow.com/module/gmat- ... /video/946
- https://www.beatthegmat.com/ratio-problem-t268339.html
- https://www.beatthegmat.com/overlapping- ... 65223.html
- https://www.beatthegmat.com/fractions-t264254.html
- https://www.beatthegmat.com/overlapping- ... 64092.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-2

Easy Data Sufficiency questions
- https://www.gmatprepnow.com/module/gmat- ... /video/943
- https://www.beatthegmat.com/for-what-per ... 70596.html
- https://www.beatthegmat.com/ds-quest-t187706.html

Medium Data Sufficiency questions
- https://www.beatthegmat.com/sets-matrix-ds-t271914.html
- https://www.beatthegmat.com/each-of-peop ... 71375.html
- https://www.beatthegmat.com/a-manufacturer-t270331.html
- https://www.beatthegmat.com/in-costume-f ... 69355.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-1

Difficult Data Sufficiency questions
- https://youtu.be/dsCeqF9Kbk8
- https://www.beatthegmat.com/double-set-m ... 71423.html
- https://youtu.be/dOZ9KM1m5Hs
- https://www.beatthegmat.com/sets-t269449.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-3

Cheers,
Brent