<p>Kidwithshirt:</p>
<p>Thanks a bunch, I understood your first explanation; I didn’t even think to look for patterns. And, if it changes anything, this isn’t a book PR puts out for the masses, you can only receive it if you take the course (it’s called Beat the SAT), at least that’s what my instructor told me. I just figured I might as well go through it, since it can’t hurt me and would be a waste of 425 pages otherwise. I’m planning to go through that, then the Blue Book, then Barron’s 2400, then if needed, Gruber’s Complete SAT Math Workbook. If doubt I’ll be able to go through all that for the May SAT, but I’ll leave the remainder over for October/November. I do agree, though, that PR is riddled with mistakes. It’s a pain, but what can I do? Only book that seems not to have them is the Blue Book.</p>
<p>As for the second problem, I see that it is 61; I should have just taken the average of the first and last terms, determining them by the formula n+10, where n is any number. I made the same mistake of thinking that 10 was the first term (I subtracted 101 from 111), which is what threw me off.</p>