Data Sufficiency

Hi,

Here is a question. I think the answer is B. But OA is D. Why , because we have the same difference of 6 shelves if we have 8 old shlelves or 9 old shelves.

a) if we had 8 shelves of 50 capacity, meaning 400 books, we need at least 14 shelves to accomodate all of these books. So we need 6 more small capacity shelves than the big capacity 1.

b) if we have 9 old shelves, total books at 450. We need 15 new ones.

The important point to note is that in the case a there will be some extra space of 20 books left on the last shelf. But there is no such restriction that there should be no free space. So I think A is not sufficient. Here is the question and the detail explanation of the OA.

Do you agreee ?

It's subtle but I think the problem states "with 30 picture books on each shelf" and implies that each shelf is full. I can see where the wording could be confusing. Your point would be much stronger if the question stated something along the lines of "shelf with capacity of 30 books"- perhaps in that case you wouldn't need to assume the shelf is full.

Thanks.

I never looked from that point of view, going so deeply. I hope the real GMAT will not have such small points, there is hardly any time to go into such minute details.