BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

GMAT exam question won't leave me alone

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
Expert replies
by SoftwareDrone » Mon Aug 13, 2012 7:52 pm
Hey, I just passed the GMAT!! :-)) CELEBRATION!!!! :-D

However..........
There was this ONE PROBLEM that keeps eating at me!
It says let x = -1. Then it gives a formula and that formula is x to the power of n plus x to the power of (n-1) plus x to the power of (n-2). So, x^n + x^(n-1) + x^(n-2). Then it says that n is the sum of all the prime numbers up to 403. WTF?????????
How am I supposed to know that?? Not fair.
I can see that if n was odd, then the answer would be -1 and if n was even, the answer would be 1. But how do they expect me to know the sum of all the prime numbers up to 403?
If there were an even number of prime numbers, and all are odd except 2, then we would have odd + odd + even = even. If there were an odd number of prime numbers, then we would have odd + odd + odd + even = odd.
????????????????????????
Join the discussion
Source: — Quantitative Reasoning |

by theCEO » Wed Aug 15, 2012 4:19 pm
What was the question asking for?
Join the discussion

by SoftwareDrone » Wed Aug 15, 2012 5:10 pm
theCEO wrote:What was the question asking for?
Sorry about that. :-)
The question was asking the value of f(x), where f(x) = x^n + x^(n-1) + x^(n-2) where n = the sum of all of the prime numbers up to 430.
If that sum is odd, then the answer would be -1 (-1 + 1 + -1). If even, then the answer would be 1 (1 + -1 + 1). The trick is finding out whether n is odd or even.
Join the discussion

by dabral » Thu Aug 16, 2012 11:54 am
SoftwareDrone,

I highly doubt that on the GMAT they would expect you to know if there are an even or an odd number of prime numbers up to say 403. This would require one to know all the prime numbers from 1 to 403, and on the GMAT they only test prime numbers less than 100. I haven't seen such a question on the GMAT so far.

However, I do expect them to test the following variants:
What is the value of (-1)^n + (-1)^(n+1) + (-1)^(n+2) where n is:

Variation#1) The product of prime numbers less than 403.

Variation#2) The sum of the first 403 prime numbers. (This is different from the sum of the prime numbers less than 403)

My guess is they asked you Variation#2.

Cheers,
Dabral
Free Video Explanations: 2021 GMAT OFFICIAL GUIDE.
Join the discussion

by SoftwareDrone » Thu Aug 16, 2012 11:59 am
dabral wrote:SoftwareDrone,
However, I do expect them to test the following variants:
What is the value of (-1)^n + (-1)^(n+1) + (-1)^(n+2) where n is:

Variation#2) The sum of the first 403 prime numbers. (This is different from the sum of the prime numbers less than 403)

Cheers,
Dabral
I had been thinking the same thing. This variant was probably the real question.
Thanks!
:-)
Join the discussion

by DFritschy » Thu Aug 16, 2012 12:16 pm
So can someone please explain the answer using the variants listed above?
Join the discussion

by dabral » Thu Aug 16, 2012 12:30 pm
DFritschy,

I will give you a hint:
How many of the first 403 prime numbers are odd and how many are even? What would be the sum of the resulting set of integers? Odd or Even? And why?

What is the value of (-1)^n + (-1)^(n+1) + (-1)^(n+2) where n is:

Variation#2) The sum of the first 403 prime numbers.

Dabral
Free Video Explanations: 2021 GMAT OFFICIAL GUIDE.
Join the discussion