BTGModeratorVI wrote: ↑

Thu Aug 27, 2020 12:03 pm

How many books will fit into a drawer?

(1) Each book has a volume of 10 cubic centimeters.
(2) The drawer is 300 centimeters by 30 centimeters by 20 centimeters and has the shape of a rectangular solid.

Answer: E
Source: GMAT prep

Target question: How many books will fit into a drawer?

Statement 1: Each book has a volume of 10 cubic centimeters.
Since we have no information about the size of the drawer, statement 1 is NOT SUFFICIENT

Statement 2: The drawer is 300 centimeters by 30 centimeters by 20 centimeters and has the shape of a rectangular solid.
Since we have no information about the size of the books, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
It's very tempting to think that, since the volume of the drawer = (300)(30)(20) = 180,000 cubic centimeters, we need only divide that this volume by the volume of one book to determine the number of books that will fit in the drawer. To better understand why this reasoning is faulty, let's examine two possible cases:
Case a: The measurements of the book are 1000 cm by 0.1 cm by 0.1 cm (notice that the volume of this book is 10 cubic centimeters). Since this book is far too long to fit into the drawer, the answer to the target question is ZERO books will fit into the drawer
Case b: The measurements of the book are 10 cm by 1 cm by 1 cm (the volume of this book is still 10 cubic centimeters). In this case, the answer to the target question is more than zero books will fit into the drawer
Since we can’t answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent