Numbers Property Strat. Guide - Chp. 2 - Odds,Evens,Pos,Negs

[clarence.booth]

Hi,

My question comes from the Num. Strat. Guide in Chp. 2, pg. 39 regarding disguised positives and negatives questions. Here is the example problem:

If a-b/c < 0, is a > b?
1. c<0
2. a+b<0

I don not understand how we determine sufficiency for statement 1. The text says: "The fact that a-b/c <0 tells you that a-b and c have different signs. Thus, one of the expressions is positive and the other is negative. Statement 1 says c is negative. Therefore, a-b must be positive."

It is the underline portion above where I lack understanding.

Thanks for the advice.

[RonPurewal]

If this/that < 0, then there are only two possibilities:
"- "this" is positive, and "that" is negative;
"- "this" is negative, and "that" is positive.

Assuming that the fraction is supposed to be (a - b)/c"”"”note that the parentheses are necessary!"”"”here we have "this" = a - b, and "that" = c.

If the expression is actually a - b/c (as you wrote), then none of this stuff works at all, so I think it's safe to assume that it's supposed to be (a - b)/c. Please correct if it's actually otherwise.

[clarence.booth]

Ron, you are right: it should be written (a - b)/c...

Having said that, the explanation makes perfect sense. Thanks again!

CB

[tim]

Cool; let us know if there are any further questions on this one!