first, thank you for making a review book that took me out of my comfort zone and makes me feel like I am starting over again. These problems are kicking my a$$, yet the information definitely feels relevant, congratulations.

Now, to the root of my frustrations:

1) Try it 4-8, page 105:

if abs(x) = abs (2Y), what is the value of X-2Y?

1) X+ 2Y = 6

2) XY>0


1 = sufficient: your explination states "you might realize that a positive sum indicates that both X and 2Y are positive"

I have spent over an hour dissecting this statement, problem, reviewing, looking back at the original guide, etc. I'm getting bogged down that a positive plus a negative can = a positive or a negative, depending on the magnitude of the values.

PLEASE set me straight here.


Question 2:

TRy it #4-9

You set up the flow chart, then state that "b^2 must be positive, therefore a is positive. How is this so, as a can be negative, yet a^2 is still positive. Please help again.


Thank you!

Gladly!

For your first question, if we know that abs(x)=abs(2y), then either x=2y or x=-(2y).

For example, either x is 4 and y is 2, x is =-4 and y=-2, x=-4 and y=2, or x=4 and y=-2.

If statement 1 says x + 2y = 6, the only case from above that works is x=4, y=2. The others will either give you 0 or a negative number. Make sense?

_________________
Jamie Nelson
ManhattanGMAT Instructor

I agree with you. I don't think there's any way that we know that a is positive just based on this statement. In fact, I subbed numbers in that fit a^2=b^2 (I used 2 for a and 2 for b, then -2 for a and 2 for b) and got different answers. I think there is an error here.

_________________
Jamie Nelson
ManhattanGMAT Instructor