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Statement 1:-

Total fiction books= 40
Hardcover fiction books= 25
So, paper-cover fiction books= 15 (40-25)

Since the total books is B and and fiction books are 40. Non fiction would be (B-40)

We don't know the value of non-fiction books (both hard cover and paper cover)
Not sufficient.

Statement 2

Hardcover books= 60
Fiction and Hardcover books= 25

So, non fiction hardcover books are= 35 (60-35)

Just as in statement 1, this statement does not give us the number of paper-cover book (both fiction and non fiction)
Not sufficient.

Combining both statements, we do not get the answer as we do not know the number of non-fiction and paper-cover books.

E is the answer
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Is this E by any chance as we dont have sufficient info about Non fiction books

it took be bloody 6 minutes to solve this question

IMO C, sorry dificult to write explaination..... waiting for OA

E for me too.

no info about Non-Fiction Paper back

Stem
FI | NF |
---------------
25 | ?? | HC
---------------
?? | ?? | PB
---------------

1)
FI | NF |
---------------
25 | ?? | HC
---------------
15 | ?? | PB
---------------
^
||
Total = 40
Insufficient

2)
FI | NF |
---------------
25 | 35 | HC <= Total = 60
---------------
?? | ?? | PB
---------------
Insufficient

Both
FI | NF |
---------------
25 | 35 | HC
---------------
15 | ?? | PB
---------------
Insufficient

E is the answer.

IMO E
info given
f | Nf |total
HC|25|-
PB|- |-
A)
f | Nf |total
HC|25|-
PB|14|-
T |40|-
Clearly not sufficient
B)
f | Nf |total
HC|25|35|60
PB|--|-
T |--|-
Insufficient

A and B combined
f | Nf |total
HC|25|35|60
PB|15|??|
T |40|??|
Still value of nonfiction paper back is not known
there not sufficient
So E
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I think you meant (60-25), not (60-35)
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IMO A...

What is the OA and OE?

The OA is E. Please refer to the solutions above and ask if anything remains unclear.
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Oh did a blunder!!

Now Got it!! Thanks Bunuel

A couple of ways to solve this question:

Venn Diagram Method: https://youtu.be/5G5IwHoHjgk
Chart Method: https://www.youtube.com/watch?v=DCn-r_4rNFI

In this kind of DS questions are fiction/non-fiction and hardcover/paperback options exhaustive? If there is no note that he has only these kinds of books, we can't assume it, right?

We cannot assume that because each of the statements clearly stated " and the rest ", implying other options could not be assumed.
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There are 4 categories of Books
P = Fiction & Hardcover
Q = Fiction & Paperback
R = Non-Fiction & Hardcover
S = Non-Fiction & Paperback

P+Q+R+S = B (given)
P = 25
Find Value of B

STMT 01: P+Q = 40
P=25 => Q = 15
P+Q+R+S = B
40+R+S = B
Since values of R & S are unknown. This stmt is insufficient.

STMT 02: P + R = 60
P=25 => R = 35
Q+S+60 = S
Since values of Q & S are unknow. This stmt is insufficient

STMT 01 & 02:
P=25 ; Q=15 ; R = 35 ; S = ?
P+Q+R+S = B
75+S = B
Still value of S is unknown. Hence E.

It also took very long for me. After giving a thought again, I realized that it can be solved very easily by a table format.
fiction Non
------------------------------------------------------------
Hardcover 25 35 from 2nd = 60
-------------------------------------------------------------
Paper 15 PF x ----- no info
-----------------------------------------------------------------
Total 40 from 1st

So E.

I completely agree that this question can be answered efficiently using a matrix box approach, also known as the double matrix. The one thing I want to add to this discussion is to answer the question: How do we know that we can use a matrix box on this question?

Whenever we see that a group can be divided into 2 parts in 2 different ways, we can use a matrix box. In this case, George's books can be divided into fiction and nonfiction (1st way) and hardcover and paperback (2nd way). This tells us that we can use a matrix box.

I hope that this helps others to more quickly recognize that a matrix box or double matrix will be useful on questions like these. If you want more practice on recognizing and using matrix boxes, please visit the following link, where I have compiled a list of questions on which you can use matrix boxes:

Matrix Boxes
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Answer is E

How do I immediately see that the following matrix is not sufficient? I though I had enough equations to solve for B Bunuel?

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