What is the value of t?

Expert replies

VJesus12: Legendary Member; Posts: 2276; Joined: Sat Oct 14, 2017 6:10 amFollowed by: 3 members

by VJesus12 » Mon Mar 19, 2018 3:42 am

What is the value of t? $$(1)\ \ \ \ \ t(t-1)^2=4t\ .$$ $$(2)\ \ \ t\ \ is\ an\ \ integer.$$ The OA is E.

Experts, using both statements is not sufficient? I think the answer should be C. Am I wrong?

Like this post

Source: Beat The GMAT — Data Sufficiency | Mon Mar 19, 2018 3:42 am

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Mon Mar 19, 2018 3:48 am

VJesus12 wrote:What is the value of t? $$(1)\ \ \ \ \ t(t-1)^2=4t\ .$$ $$(2)\ \ \ t\ \ is\ an\ \ integer.$$ The OA is E.

Experts, using both statements is not sufficient? I think the answer should be C. Am I wrong?

Statements combined:
Test easy integer values for t (0, 1, 2, 3, etc.).
t(t-1)Â² = 4t is satisfied by both t=0 and t=3.
Since t can be different values, INSUFFICIENT.

The correct answer is E.

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

Like this post

Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 amFollowed by: 22 members; Location: New York, NY; Thanked: 39 times

by Jeff@TargetTestPrep » Mon Mar 26, 2018 4:53 pm

VJesus12 wrote:What is the value of t? $$(1)\ \ \ \ \ t(t-1)^2=4t\ .$$ $$(2)\ \ \ t\ \ is\ an\ \ integer.$$

We need to determine the value of t.

Statement One Alone:

t(t - 1)^2 = 4t

Simplifying we have:

t(t^2 - 2t + 1) = 4t

t^3 - 2t^2 + t = 4t

t^3 - 2t^2 - 3t = 0

t(t^2 - 2t - 3) = 0

t(t - 3)(t + 1) = 0

t = 0 or 3 or -1

Statement one alone is not sufficient to answer the question.

Statement Two Alone:

t is an integer

Statement two alone is not sufficient to answer the question.

Statements One and Two Together:

Using both statements we still see that t = 0 or 3 or -1.

Answer: E

Jeffrey Miller
Head of GMAT Instruction
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 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