I have with me "
Manhattan GMAT Fractions, Decimals, & Percents 5th Edition". At the end of the book, there's a list of practice problems that you have to go fetch from "The Official Guide for GMAT Review 13th Edition" and "The Official Guide for GMAT Quantitative Review 2nd Edition". However, it appears that the numbered problems in the Manhattan book do not match with the problems in the Official Guide.
For example, the Manhattan book claims that the very first problem on its list, problem number 17 in "The Official Guide for GMAT Review 13th Edition", is supposed to be about "Digits and Decimals"; however, in the Official Guide, it's actually about roots. The actual problem reads: "If n = √(16/81), what is the value of √n?".
Yes, I'm pretty sure I'm holding the right editions of each book; it says so on their PDF covers. What's going on?