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 Author: questioner [ Thu Feb 03, 2011 9:19 pm ] Post subject: GMAT Algebra If x³ > y² > z, which of the statements could be true?I. x < y < zII. x < z < yIII. y < x < zA. I onlyB. III onlyC. I and II onlyD. II and III onlyE. I, II and III(E) Choice I is possible: x = 3, y = 4, z = 5Choice II is possible: x = 3, y = 5, z = 4Choice III is possible: x = 4, y = 3, z = 6The correct answer is E.----------Is there any other method to solve this question?How can I choose the figure to plug in?

 Author: Gennadiy [ Fri Feb 04, 2011 2:30 pm ] Post subject: Re: math (test 5, question 36): inequalities This is a tough question indeed and requires laconic reasoning.When we deal with exponents and inequalities the usual things to keep in mind are the properties of powers:x³ > y² > z1. negative/zero/positiveAny square is a non-negative number, while any cubed number has the same sign as the number itself.Since x³ > y² and y² is a non-negative number, then x³ > 0 and so x > 0. On the other hand, y can be positive or negative while y² will still have the same value.2. greater than 1 / 1 / greater than 1If 0< x < 1 then x³ < x² < xIf x = 1 then x³ = x² = x = 1.If x > 1 then x³ > x² > xNow, keep in mind those properties and analyze the options one-by-one. We try to fix such values that fit or find a contradiction along the way. Let's start with the easiest one.x³ > y² > zIII. y < x < zSince x is positive so is z. Remember, that y can be positive or negative, while y² remains the same. If y is negative, then y < x holds.Now, consider the second part: x < z. On the other hand the original statement defines x³ > z. So x < z < x³. So we must pick a number for x and then pick z within the range. If x = 2, then 2 < z < 8. Let z be 3.So 8 > y² > 3. Let y be -2. Therefore the option III can be true.x³ > y² > zI. x < y y² > zII. x < z < yThis is the toughest one, but we use the same logic.x < z < y² < x³ and z < yLet's fix the value of x first. Let it be 3.3 < z < y² < 27 and z < yLet y be 5. 3 < z < 25 < 27 and 3 < z < 5. z can be 4. Therefore the option II can be true.Though it might seem to be quite long in writing, it's not that long in reasoning, especially when you have skills in dealing with inequalities and keep in mind the properties described in the beginning.

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