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Errors in the GMAT Official Guide, Part 2
Posted by ian on Thu 09 Oct 08 at 9:01pm
In an earlier post, Michael described a few of the mistakes that could be found in earlier printings of the 11th Edition of the Official Guide to GMAT Review. In my version of the book, the 6th printing, many errors have been corrected, but a few remain. Still, the number of errors in the book is remarkably small, considering how much the book contains. In any case, there are at least three mistakes:
page 62, solution to Q44. When analyzing Statement (2), they write "For example, if root(m) = 1/4..." but the question stem states that m is a positive integer, so it's impossible for root(m) to be equal to 1/4, and the example is irrelevant. The logic is otherwise essentially correct; by choosing n=1 and m=2, for example, it is easy to demonstrate that the expression in question does not need to be an integer.
page 252, solution to Q201. The question says that the sum of n consecutive integers is 0. In the solution to the problem, they write "Therefore, because in this case the sum of n consecutive integers will always consist of the single number 0 plus these pairs of negative and positive integers, the sum of n consecutive integers has to be an odd number." The end of this sentence is incorrect, quite clearly we know the sum of the n integers is equal to zero, which is an even number, not an odd number. The sentence should instead read as follows: "Therefore, because in this case the sum of n consecutive integers will always consist of the single number 0 plus these pairs of negative and positive integers, n has to be an odd number."
page 327, solution to Q118. When they consider both statements together, they write "Taking (1) and (2) together, n could only be 1, 2, 3, and 5 ..." From Statement (2), n is prime, so there's no way n could be equal to 1 (1 is not a prime number). n can only be 2, 3 or 5.
If we find any other significant errors in official GMAT materials, we'll be sure to report them here.


