GmatPrep I--x^4 + y^4 = 100

Expert replies

prachich1987: Legendary Member; Posts: 752; Joined: Sun Sep 12, 2010 2:47 amFollowed by: 10 members; Thanked: 20 times; GMAT Score:700

by prachich1987 » Sat Jan 01, 2011 11:40 pm

If x^4 + y^4 = 100, the greatest possible value of x is between

a. 0 and 3
b. 3 and 6
c. 6 and 9
d. 9 and 12
e. 12 and 15

Like this post

Source: Beat The GMAT — Problem Solving | Sat Jan 01, 2011 11:40 pm

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sun Jan 02, 2011 12:22 am

prachich1987 wrote:If x^4 + y^4 = 100, the greatest possible value of x is between

a. 0 and 3
b. 3 and 6
c. 6 and 9
d. 9 and 12
e. 12 and 15

(x^4 + y^4) = 100 => x^4 = (100 - y^4)

Note that when x is maximum, x^4 is also maximum. Now to maximize x we have to maximize (100 - y^4), which is equivalent to minimization of y^4. Now minimum value of y^4 is 0. Therefore maximum value of (100 - y^4) is 100.

Thus, maximum value of x^4 is 100.
Therefore, maximum value of x = 4-th root of 100 = âˆš10 â‰ˆ 3.(something)

The correct answer is B.

Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Like this post

prachich1987: Legendary Member; Posts: 752; Joined: Sun Sep 12, 2010 2:47 amFollowed by: 10 members; Thanked: 20 times; GMAT Score:700

by prachich1987 » Sun Jan 02, 2011 12:27 am

Thanks Anurag.
Even I had marked B.
But the answer given in the document is A.It must be wrong.

Like this post

GMAT/MBA Expert

lunarpower: GMAT Instructor; Posts: 3380; Joined: Mon Mar 03, 2008 1:20 amFollowed by: 1535 members; Thanked: 2256 times; GMAT Score:800

by lunarpower » Sun Jan 02, 2011 1:22 am

prachich1987 wrote:Thanks Anurag.
Even I had marked B.
But the answer given in the document is A.It must be wrong.

yep

i noticed that you titled this thread "gmatprep I" -- did you actually see this problem on gmatprep, with this solution, with your own two eyes? or did you get it from some kind of archive?

Ron has been teaching various standardized tests for 20 years.

--

Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions Ã Ron en franÃ§ais
Voit esittÃ¤Ã¤ kysymyksiÃ¤ Ron:lle myÃ¶s suomeksi

--

Quand on se sent bien dans un vÃªtement, tout peut arriver. Un bon vÃªtement, c'est un passeport pour le bonheur.

Yves Saint-Laurent

--

Learn more about ron

Like this post

prachich1987: Legendary Member; Posts: 752; Joined: Sun Sep 12, 2010 2:47 amFollowed by: 10 members; Thanked: 20 times; GMAT Score:700

by prachich1987 » Sun Jan 02, 2011 1:24 am

lunarpower wrote:
prachich1987 wrote:Thanks Anurag.
Even I had marked B.
But the answer given in the document is A.It must be wrong.
yep

i noticed that you titled this thread "gmatprep I" -- did you actually see this problem on gmatprep, with this solution, with your own two eyes? or did you get it from some kind of archive?

This is from the document "198 Level 700+ questions from GMAT Prep I which I downloaded from BTG.

Like this post

GMAT/MBA Expert

lunarpower: GMAT Instructor; Posts: 3380; Joined: Mon Mar 03, 2008 1:20 amFollowed by: 1535 members; Thanked: 2256 times; GMAT Score:800

by lunarpower » Sun Jan 02, 2011 1:41 am

prachich1987 wrote:
lunarpower wrote:
prachich1987 wrote:Thanks Anurag.
Even I had marked B.
But the answer given in the document is A.It must be wrong.
yep

i noticed that you titled this thread "gmatprep I" -- did you actually see this problem on gmatprep, with this solution, with your own two eyes? or did you get it from some kind of archive?
This is from the document "198 Level 700+ questions from GMAT Prep I which I downloaded from BTG.

ah. ok.

i downloaded it and wrote a post about it here:
https://www.beatthegmat.com/198-level-70 ... tml#327982

there are a couple of other sketchy problems in there -- for instance, #74 says that two INTEGERS x and y have a sum of 72, but statement (1) says that x = y + 1. this is impossible; if x = y + 1 and x+y = 72, then you get x = 36.5 and y = 35.5, contradicting the statement that they are integers.
so, overall, that's a decent source, but (a) be careful, and (b) they aren't all "top difficulty" problems (not that this matters anyway -- it doesn't).
in fact, any claim by anyone who purports to know the exact difficulty levels of official GMAC problems will always be a lie; GMAC has never published the adaptive performance curves of any of its problems, nor does it ever plan to do so.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review