Quantitative Reasoning

Hey guys...

I ran into three questions in GMAT Prep 2 that I couldn't quite master even when I saw the answer...

1) I had to attach it because it involves geometry and I couldn't replicate the figure. I have no idea how to get the answer which is D (EACH statement is sufficient). I can solve the problem using both statements quite easily.

2) I can solve this with a calculator (not allowed) or by hand but it takes WAY too long to be sufficient at solving problems quickly. Does anyone have any shortcuts/ hints to approximating...

(1001^2)-(999^2) / (101^2)-(99^2)
(the first part divided by the second)

a) 10
b) 20
c) 40
d) 80
e) 100

Again I know how to get the answer (A)...I just need to get it faster



3)
if w+x < 0
is w + y > 0?

I) x+y > 0
II) y< x < w

a) I is suff.
b) II is suff.
c) BOTH
d) EACH
e) neither

answer is B and I can do it but it takes me awhile.... A concise explanation that would help on future problems would be helpful...thanks guys