This is a question from the powerprep testing software the GMAT used to offer.

Currently there are 50 picture books on a shelf in the children's section of a library. IF these books were to be placed on smaller shelves with 30 picture books on each shelf how many of the smaller shelves would be needed to hold all of these books?

(1) The number of smaller shelves needed is 6 more than the current number of shelves.

(2) Currently there are 9 shelves in the children's section.


I say that the answer is B, 2 only.

The explanation from the powerprep states that:

1 yields the equation --> 30(s+6) = 50s therefore s = 9 end of story.
Obivously 2 works. SO they say each alone is fine.

WHen i worked the problem i agree 9 works, but so does 8. If you have 8 rows of books originally you have 50(8)= 400 books. For 400 books to be distributed on shelves of 30 books each you would need 400/30 = 13.333333 shelves, which mean you'd need 14 shelves (you can't have 1/3 of a shelf). 14 = 8+6. Statement 1 is valid for both 9 and 8, therefore you can't solely use it.

how am i wrong here?