Comprehensive Prep for GMAT Data Sufficiency. Every year, students pay 1,000 and more to test prep companies to prepare for the math section of the GMAT. Now you can get the same preparation in a book. Features: Comprehensive Review: Twenty-four chapters provide the most thorough review of data sufficiency math available. Practice: Includes 196 examples and more than 205 exercises!. Performance: If your target is 700+ score, this is the book.