Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

I couldn't figure out using statement 1 so I ignored it to start with. Using statement 2, x|x| will always be < 2^x. So the answer is either B or D.

Going back to statement 1, I plugged in negative values such as -1, -2 and also fractions and realised that if x is not an integer, the result need not always be true but if x is an integer, x|x| will always be < 2^x. And the question stem does say that x is an integer.

Hence D for me. _________________

Try and try until you succeed! There is just no giving up!

I solved it - using two options -10 |10| < 1/2^10 AND -10 -|10| < 1/2^10. This method gives two solutions and therefore not sufficient. However my logic is wrong. Please explain why there are not two options. I have come across questions where one is required to use the two options. why not in this case? thanks

I solved it - using two options -10 |10| < 1/2^10 AND -10 -|10| < 1/2^10. This method gives two solutions and therefore not sufficient. However my logic is wrong. Please explain why there are not two options. I have come across questions where one is required to use the two options. why not in this case? thanks

If x is an integer, is x*|x|<2^x

This is YES/NO data sufficiency question: In a Yes/No Data Sufficiency question, each statement is sufficient if the answer is “always yes” or “always no” while a statement is insufficient if the answer is "sometimes yes" and "sometimes no".

Now, you should notice that the RHS (right hand side) of the expression is always positive (\(2^x>0\)), but the LHS is positive when \(x>0\) (\(x>0\) --> \(x*|x|=x^2\)), negative when \(x<0\) (\(x<0\) --> \(x*|x|=-x^2\)) and equals to zero when \(x={0}\).

(1) x<0 --> according to the above \(x*|x|<0<2^x\), so the answer to the question "is x*|x|<2^x" is YES. Sufficient.

(2) x=-10, the same thing here \(x*|x|=-100<0<\frac{1}{2^{10}}\), so the answer to the question "is x*|x|<2^x" is YES. Sufficient.

Answer: D.

cmugeria wrote:

-10 |10| < 1/2^10 AND -10 -|10| < 1/2^10.

When \(x=-10\) then \(|x|=|-10|=10\) and \(x*|x|=-10*10=-100\).

In an inequality you can't move variables from side to side using multiplication or division unless you know their sign since the inequality expression will change direction if you multiply or divide both sides by a negative number.

Both statements tell you that X is negative, so you know that you can now divide both sides by X, giving you a definite equation that |x| > (2^x)/X

Please help me understand what the difference (in regards to having two solutions in terms of absolute and non absolute values) is between the two questions is x*|x|<2^x and the question |x+1|= x*|3x-2|what are the possible values for x from advanced equations of MGMAT Equations and inequalities - the answer is 1/4 and 3/2

Please help me understand what the difference (in regards to having two solutions in terms of absolute and non absolute values) is between the two questions is x*|x|<2^x and the question |x+1|= x*|3x-2|what are the possible values for x from advanced equations of MGMAT Equations and inequalities - the answer is 1/4 and 3/2

Maybe i am overanalyzing the questions

I don't quite understand your question.

Original question asks whether \(x*|x|<2^x\) is true, it's YES/NO DS question, it doesn't ask for specific value of \(x\). AGAIN: In a Yes/No Data Sufficiency question, each statement is sufficient if the answer is “always yes” or “always no” while a statement is insufficient if the answer is "sometimes yes" and "sometimes no". As EACH statement ALONE gives the definite answer YES x*|x| is less than 2^x then EACH statement ALONE is sufficient to answer the question which means than answer is D .

Another one \(|x+1|=|3x-2|\) (I believe it's \(|x+1|=|3x-2|\) and not |x+1|= x*|3x-2| as you wrote, as solutions you provided 1/4 and 3/2 satisfy the first equation and not the second one), seems to be another type of DS question, the one which asks for a certain value of an unknown. For this type of questions statement is sufficient if it gives single numerical value of this unknown. So as \(|x+1|=|3x-2|\) has two solutions \(x=\frac{1}{4}\) and \(x=\frac{3}{2}\) then this statement (if this is the only thing we know for certain statement) is not sufficient, as it does not give single numerical value of \(x\).

Re: If x is an integer, is x|x| < 2^x? [#permalink]
12 Sep 2014, 07:47

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Hello everyone! Researching, networking, and understanding the “feel” for a school are all part of the essential journey to a top MBA. Wouldn’t it be great... ...

Are you interested in applying to business school? If you are seeking advice about the admissions process, such as how to select your targeted schools, then send your questions...