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If Z>-8,Z may be any value b/t -7 to infinity then -2<Z<8 condition will fail.

We are told that -2<z<8, so this statement is GIVEN to be true. For example z might be -1, 0, 1.5, 5, ... ANY value of z from this (true) range -2<z<8 will be more than -8.

So when you say that z might for example be -7 it's not true as -2<z<8.

To elaborate more. Question uses the same logic as in the examples below:

If x=5, then which of the following must be true about x: A. x=3 B. x^2=10 C. x<4 D. |x|=1 E. x>-10

Answer is E (x>-10), because as x=5 then it's more than -10.

Or: If -1<x<10, then which of the following must be true about x: A. x=3 B. x^2=10 C. x<4 D. |x|=1 E. x<120

Again answer is E, because ANY x from -1<x<10 will be less than 120 so it's always true about the number from this range to say that it's less than 120.

Or: If -1<x<0 or x>1, then which of the following must be true about x: A. x>1 B. x>-1 C. |x|<1 D. |x|=1 E. |x|^2>1

As -1<x<0 or x>1 then ANY x from these ranges would satisfy x>-1. So B is always true.

Her weight is more than 120 pounds but less than 130 pounds. Then which of the following is definitely true about her weight? A. Her weight is 125 pounds. B. Her weight is more than 110 pounds.

Isn't statement B definitely true about her weight? Since I know her weight is between 120 and 130 pounds, it is more than 110 pounds. _________________

If it is true that z < 8 and 2z > -4, which of the following [#permalink]
11 Jan 2013, 08:26

If it is true that z < 8 and 2z > -4, which of the following must be true? (A) -8 < z < 4 (B) z > 2 (C) z > -8 (D) z < 4 (E) None of the above

It's a relatively easy question. However, the answer and explanation provided by Sackmann are totally confusing. Curious to know what you guys will come up with.

Edit: Something went wrong with the >< and (-), updated the question. Source: Total GMAT _________________

Re: If it is true that z < 8 and 2z > -4, which of the following [#permalink]
11 Jan 2013, 11:09

1

This post received KUDOS

Expert's post

megafan wrote:

If it is true that z < 8 and 2z > -4, which of the following must be true? (A) -8 < z < 4 (B) z > 2 (C) z > -8 (D) z < 4 (E) None of the above

It's a relatively easy question. However, the answer and explanation provided by Sackmann are totally confusing. Curious to know what you guys will come up with.

Edit: Something went wrong with the >< and (-), updated the question. Source: Total GMAT

Merging similar topics. Please refer to the solutions above. _________________

Re: If it is true that z < 8 and 2z > -4, which of the following [#permalink]
11 Jan 2013, 15:30

Awesome! thanks for merging with this post. Your examples above—http://gmatclub.com/forum/if-it-is-true-that-z-8-and-2z-4-which-of-the-following-105709.html#p826787 cleared up my confusion. I was thinking in a completely different way. Now it makes sense that you want to pick a solution that covers all the possible values of X—and that's pretty much all this is, it's so simple when you realize it! _________________