IS t^2 > t/3?

This topic has expert replies
Source: — Data Sufficiency |

User avatar
MBA Admissions Consultant
Posts: 2279
Joined: Fri Nov 11, 2011 7:51 am
Location: New York
Thanked: 660 times
Followed by:266 members
GMAT Score:770

by Jim@StratusPrep » Mon Mar 19, 2012 6:40 am
You are simply squaring the denominator on the left and multiplying the denominator of t by 3 on the right. 1/3 is an inflection point where t^2 will be bigger if t is > 3. Absolute value works because the left will always be positive, the right will not.

Answer c
GMAT Answers provides a world class adaptive learning platform.
-- Push button course navigation to simplify planning
-- Daily assignments to fit your exam timeline
-- Organized review that is tailored based on your abiility
-- 1,000s of unique GMAT questions
-- 100s of handwritten 'digital flip books' for OG questions
-- 100% Free Trial and less than $20 per month after.
-- Free GMAT Quantitative Review

Image

Master | Next Rank: 500 Posts
Posts: 234
Joined: Fri Oct 01, 2010 7:28 pm
Location: chennai
Thanked: 5 times
Followed by:4 members

by pappueshwar » Mon Mar 19, 2012 7:06 am
jim,
request to explain stmtnt 1 again with example.
sorry.

User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Mar 19, 2012 8:10 am
pappueshwar wrote:IS t^2 > t/3?

1) t>0
2) |t|>1/3

OA IS B. heavily confused
t² > t/3
3t² > t
3t²-t > 0
t(3t-1) > 0.

The lefthand side is equal to 0 if t=1 or t=1/3.
These are the CRITICAL POINTS: the values where t²=t/3.
When t is ANY OTHER VALUE, t²>t/3 or t²<t/3.
To determine the range where t²>t/3, test one value to the left and right of each critical point.

t<0:
Let t=-1.
(-1)² > 1/3.
1 > 1/3.
This works.
Thu, t<0 is part of the range where t² > t/3.

0<t<1/3:
Let t=1/4.
(1/4)² > (1/4)/3.
1/16 > 1/12.
Doesn't work.
Thus, 0<t<1/3 is not part of the range where t² > t/3.

t>1/3:
Let t=1.
(1)² > 1/3.
1 > 1/3.
This works.
Thus, t>1/3 is part of the range where t² > t/3.

Thus, the only range where it is NOT true that t² > t/3 is 0≤t≤1/3.

Question rephrased: Is 0≤t≤1/3?

Statement 1: t>0

No way to determine whether 0≤t≤1/3.
INSUFFICIENT.

Statement 2: |t|>1/3
Thus, it is not possible that 0≤t≤1/3.
SUFFICIENT.

The correct answer is B.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3

Master | Next Rank: 500 Posts
Posts: 234
Joined: Fri Oct 01, 2010 7:28 pm
Location: chennai
Thanked: 5 times
Followed by:4 members

by pappueshwar » Mon Mar 19, 2012 8:27 am
thanks mitch that was amazing