GMATprep sticky one: Anyone got a solution?

[madhuravkale]

Hi,

I just gave my first GMATprep yesterday. Came across one particular sum that I really got stuck onto even in the exam (I normally don't give time to questions that take too much time). So here goes:

1.) Given x>y2>z4 (numbers indicating powers), which of the following could be true?
I. x>y>z
II. z>y>x
III. x>z>y

A. I only
B. I and II only
C. I and III only
D. II and III only
E. I, II and III


After a while.[/spoiler]

[GMATGuruNY]

Hi,

I just gave my first GMATprep yesterday. Came across one particular sum that I really got stuck onto even in the exam (I normally don't give time to questions that take too much time). So here goes:

1.) Given x>y2>z4 (numbers indicating powers), which of the following could be true?
I. x>y>z
II. z>y>x
III. x>z>y

A. I only
B. I and II only
C. I and III only
D. II and III only
E. I, II and III


After a while.[/spoiler]

Ask yourself what the question is testing.
What kind of number gets smaller when it's raised to a power?
A positive fraction.

I. Let x=1/3, y=1/4, z=1/5.
Plugging these values into x > y² > z�, we get:
1/3 > (1/4)² > (1/5)�. This works.
Eliminate any answers that don't include I.
Eliminate D.

II. Let z=1/3, y=1/4, x=1/5.
Plugging these values into x > y² > z�, we get:
1/5 > (1/4)² > (1/3)�. This works.
Eliminate any remaining answers that don't include II.
Eliminate A and C.

III. Let x=1/3, z=1/4, y=1/5.
Plugging these values into x > y² > z�, we get:
1/3 > (1/5)² > (1/4)�. This works.
Eliminate any remaining answers that don't include III.
Eliminate B.

The correct answer is E.

Awhile back I wrote an article about what to do when you don't know what to do. Please feel free to check it out:

https://www.beatthegmat.com/mba/2010/07/ ... k-yourself

[amit2k9]

let x,y,z be 0.1,0.2 and 0.3 not in specific order though.

then
1 x>y>z means x 0.3 y 0.2 z 0.1 so x>y^2 > z^4. true.

3 x>z>y means x 0.3 z 0.2 y 0.1 so x>y^2 > z^4. true.

2 z>y>x mean z 0.3 y 0.2 x 0.1 so x>y^2 > z^4. true. (you can check for the values)

thus E it is.