the bookshelves break

[sanju09]

A total of b books are divided evenly among 12 bookshelves. If 2 of the bookshelves break, and the books are divided evenly among the remaining bookshelves, how many more books, in terms of b, does each of the remaining bookshelves hold?
A. b/2
B. b/10
C. b/12
D. b/20
E. b/60


OA E

[Brent@GMATPrepNow]

A total of b books are divided evenly among 12 bookshelves. If 2 of the bookshelves break, and the books are divided evenly among the remaining bookshelves, how many more books, in terms of b, does each of the remaining bookshelves hold?
A. b/2
B. b/10
C. b/12
D. b/20
E. b/60


OA E

The quickest way to solve this is to assign a "nice" value to b.
By "nice" I mean a number that we can divide by 12 and by 10.
One such number is 60 (although 120 and other numbers would work as well)
If b=60, then each of the 12 shelves will hold 5 books each.
When 2 shelves break, the 60 books are distributed among 10 shelves, so each shelf holds 6 books.
There is 1 extra book per shelf.
Now plug b=60 into each answer choice and see which one yields 1
Since E gives us 60/60 = 1, it is the correct answer.