## Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

Forum for the GRE subject test in mathematics.
PieceOfPi
Posts: 25
Joined: Mon Aug 02, 2010 3:16 pm

### Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

Hi,

I just finished working on the problems on the chapter 7 (Additional Topics) of The Princeton Review's "Cracking..." book (4th edition), and maybe it is possible that I am wrong, but I think I found a few typos in this set of problems. So I was wondering if anybody who owns this book could check if what I have are the honest-to-god typos.

(Please keep in mind that some of these might be my errors, and if that's the case, please let me know because that would be very helpful!)

#21: I don't think A or (B and C) is equivalent of saying (A and B) or (A and C) (which gives two right answers on this problem).

#22: I'm not fully convinced why Graph I and Graph II are not isomorphic. Can't we have vertices like A<-->E, B<-->G, C<-->F, and D<-->H, and place the edges similarly? (i.e. AB <--> EG, BC <-->GF, CD <--> FH)

#26: v(x, y) given in the problem doesn't look harmonic to me, and there is a different function on the solution (which looks harmonic).

#27: The third term of the fifth line of pg. 398 (the solution of this problem) should look lim_{z \to -i} [(z+1)/(z+3)(z-i)] instead of lim_{z \to -i} [(z+1)/(z+3)(z^2-i)]. I also didn't get the answer they had in the option.

#32: On the solution, I should get 64/4 + 8c instead of 64/4 + 6c. I also didn't get the answer they had in the option.

#38: Why does P(X \leq 2) = [(3^2-2)/3^2], and something similar for P(Y \leq 2)?

#44: No, you can't flip a fair coin 10 times and expect to get 40-50 heads. Change this to 100 (as in solution).

#46: Again, different answer in the solution than what is given in the option.

Thanks!

PP

angelabrookss
Posts: 3
Joined: Mon Aug 30, 2010 6:29 pm

### Re: Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

Its nice to see this !
Thanks for sharing the post !

littleface91
Posts: 1
Joined: Tue Oct 01, 2013 1:23 pm

### Re: Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

I had the same answers as you for #21 and #22. I'm confirming with someone else taking the test, but I'm thinking it is an error in the book.

Ryker
Posts: 74
Joined: Mon Jul 08, 2013 11:27 pm

### Re: Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

littleface91 wrote:I had the same answers as you for #21 and #22. I'm confirming with someone else taking the test, but I'm thinking it is an error in the book.
I already returned the book, so I don't remember what I had for question 21, but I distinctly remember thinking that graph isomorphism solution must be wrong. I guess that would be question 22 then.

Zyh3n
Posts: 1
Joined: Tue Oct 08, 2013 8:52 pm

### Re: Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

I checked with a graph theorist I know. The solution is wrong. All three of the graphs are isomorphic.

boo78
Posts: 36
Joined: Tue Oct 15, 2013 3:53 pm

### Re: Possible errors in the ch 7 of PR's "Cracking..." (4 ed)

I have gone through this text thoroughly (currently using it to teach a high school survey course), and I have identified 23 errors to date, including many in Ch. 7. I think it's a good text for seeing what you need to review the most and lots of practice problems, but you have to know your stuff to avoid being totally confused in some places.