Hello,
I'm using OG 12th edition to study, and I believe I may have found an error with DS problem 170 on page 349.
If n is a positive integer, is n^3 - n divisible by 4?
1) n = 2k + 1, where k is an integer.
2) n^2 + n is divisible by 6.
The book claims that the answer is A - statement 1 is sufficient. That seems incorrect. If you evaluate k as 0, n=1 as per statement 1. Then (1)^3 - 1 is not divisible by 4. However, you can clearly make the statement true by choosing a different k. Try k=2. n becomes 5, and n^3 - n is 120. 120 is divisible. One can make the statement true or false by choosing 1 or 2 for k, so statement 1 seems insufficient. There's no indication in statement 1 of k being positive, negative, or zero. So, it seems well within the bounds of the problem to chose either 0 or 1.
Am I missing something?
I'm using OG 12th edition to study, and I believe I may have found an error with DS problem 170 on page 349.
If n is a positive integer, is n^3 - n divisible by 4?
1) n = 2k + 1, where k is an integer.
2) n^2 + n is divisible by 6.
The book claims that the answer is A - statement 1 is sufficient. That seems incorrect. If you evaluate k as 0, n=1 as per statement 1. Then (1)^3 - 1 is not divisible by 4. However, you can clearly make the statement true by choosing a different k. Try k=2. n becomes 5, and n^3 - n is 120. 120 is divisible. One can make the statement true or false by choosing 1 or 2 for k, so statement 1 seems insufficient. There's no indication in statement 1 of k being positive, negative, or zero. So, it seems well within the bounds of the problem to chose either 0 or 1.
Am I missing something?
