computer-bot Posted April 13, 2015 Share Posted April 13, 2015 http://www.www.urch.com/forums/attachment.php?attachmentid=7025&stc=1 Quote Link to comment Share on other sites More sharing options...
Brent Hanneson Posted May 20, 2015 Share Posted May 20, 2015 http://www.www.urch.com/forums/attachments/gre-math/7025-inequality-question-solved-but-cant-confirm-math.png Nice question. Start with 4x - 12 > x + 9 Subtract x from both sides to get: 3x - 12 > 9 Add 12 to both sides to get: 3x > 21 Divide both sides by 3 to get: x > 7 The correct answer is A Here's why: If x > 7,then x MUST be greater than 6 (and the question asks what MUST be true?) Many students will choose answer choice B, because it looks very similar to x > 7 However, if x > 7 then x COULD equal 7, but answer choice B says that x must be greater than 7 So, answer choice B need not be true Cheers, Brent Quote Link to comment Share on other sites More sharing options...
computer-bot Posted May 21, 2015 Author Share Posted May 21, 2015 Thank you for such a detailed answer. However, what I don't understand is that when we say that x>=7 then the possible valueset for x is {7, 7.0000...001, ......}. But with choice A the possible value set for x is {6.0000...001, 6.0000...002, ......}. Only if we were to assume that x is an integer then option A would be correct. But this assumption is not stated in the question. Kindly clarify that? Quote Link to comment Share on other sites More sharing options...
Brent Hanneson Posted May 21, 2015 Share Posted May 21, 2015 Here's another way to put it: Let's say that Al is at least 30 years old. This means that he could be 30, 31, 32, 33, etc.... A rule at the local amusement park says that people must be older than 10 years old to ride a certain ride. Does Al qualify to ride the ride? Yes, because we can conclude with certainty that Al's age is greater than 10. Does this mean that Al could be 11? No. However, knowing that Al's age is greater than or equal to 30 means that Al's age MUST be greater than 10. The same applies to this question. If x > 7, then it MUST be true that x is greater than 6. This doesn't mean that x could equal 6.1. It just means that x is greater than 6 Cheers, Brent Quote Link to comment Share on other sites More sharing options...
prashant18 Posted June 19, 2015 Share Posted June 19, 2015 Amazing approach. Totally got the point. I took some sectional tests in GRE and found out that I have considerably low scores in inequality section now I get why. Thanks can you point out some important material that can help me with inequalities. I am struggling a lot with this topic. Thanks. Quote Link to comment Share on other sites More sharing options...
Brent Hanneson Posted July 23, 2015 Share Posted July 23, 2015 Thanks can you point out some important material that can help me with inequalities. I am struggling a lot with this topic. Thanks. Videos #38 to 45 at GRE Algebra and Equation Solving | Greenlight Test Prep cover all types of inequalities. All videos in our course are free, so check them out. Cheers, Brent - Greenlight GRE Quote Link to comment Share on other sites More sharing options...
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