Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
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.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
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 Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart 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

Easy Average problem or is it?

Expert replies
by faraz_jeddah » Thu Sep 19, 2013 11:34 pm
If the terms of a sequence t1, t2, ....tn, what is the value of n?
1. The sum of the n terms is 3,124.
2. The average (arithmetic mean) of the n terms is 4.

I was going through this problem and the obvious answer looks like C.

But I wanted to check if I were to replicate this problem on a smaller scale.

What if the problem were restated as

1. the sum of the terms is 9
2. The average is 3


In this case
I could say the series is 0,1,8 where sum is 9 and average is 3. ==> n = 3

I could also say the series is 1,2,3,3 where sum is 9 and average is 3 but n = 4.

My question is what is the impact of the word "series" in the question?
Am I overthinking this simple problem?
A good question also deserves a Thanks.

Messenger Boy: The Thesselonian you're fighting... he's the biggest man i've ever seen. I wouldn't want to fight him.
Achilles: That's why no-one will remember your name.
Join the discussion
Source: — Problem Solving |

by vinay1983 » Thu Sep 19, 2013 11:48 pm
faraz_jeddah wrote:If the terms of a sequence t1, t2, ....tn, what is the value of n?
1. The sum of the n terms is 3,124.
2. The average (arithmetic mean) of the n terms is 4.

I was going through this problem and the obvious answer looks like C.

But I wanted to check if I were to replicate this problem on a smaller scale.

What if the problem were restated as

1. the sum of the terms is 9
2. The average is 3


In this case
I could say the series is 0,1,8 where sum is 9 and average is 3. ==> n = 3

I could also say the series is 1,2,3,3 where sum is 9 and average is NOT 3 BUT 9/4 2.25 but n = 4.

My question is what is the impact of the word "series" in the question?
Am I overthinking this simple problem?
Good to see you back. I changed the average from 3 to 2.25. Happens:)

Series gives us a concrete idea about the numbers we should consider. Like in the above question you have posted, if it would have been" terms, which are positive and in series (such as A.P or G.P) would gives us definite numbers to work with.Also I feel the no. of numbers is restricted by the average. In this case to get 3 as average we should have N numbers such that we get a integer as a result. Otherwise the whole thing would be not of use to calculate.

It's a good point though, that you have raised!

Hope I am right!

For the question above, my answer is C :)
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
Join the discussion

by faraz_jeddah » Thu Sep 19, 2013 11:54 pm
vinay1983 wrote: Good to see you back. I changed the average from 3 to 2.25. Happens:)

Series gives us a concrete idea about the numbers we should consider. Like in the above question you have posted, if it would have been" terms, which are positive and in series (such as A.P or G.P) would gives us definite numbers to work with.Also I feel the no. of numbers is restricted by the average. In this case to get 3 as average we should have N numbers such that we get a integer as a result. Otherwise the whole thing would be not of use to calculate.

It's a good point though, that you have raised!

Hope I am right!

For the question above, my answer is C :)
Oh man I feel embarrassed now. The average is indeed 2.25.

Thanks Vinay!
A good question also deserves a Thanks.

Messenger Boy: The Thesselonian you're fighting... he's the biggest man i've ever seen. I wouldn't want to fight him.
Achilles: That's why no-one will remember your name.
Join the discussion

by theCodeToGMAT » Fri Sep 20, 2013 12:18 am
ANSWER [spoiler][C][/spoiler]
My Steps :
Statement 1:
( _ + _ + _ + _ + _ ) = 9

Statement 2:
( _ + _ + _ + _ + _ )/n = 3

( _ + _ + _ + _ + _ ) = 3n

Combining both
3n = 9 --> n = 3


Answer to your query:

You have made a small mistake in the second case

1,2,3,3 --> Sum = 9 BUT MEAN = 9/4=2.25
To have an average as 3 with "4 terms" you would need sum as 12; Doing so will affect statement 1
So, the series with 4 numbers is not Possible


hence, you Case 1: 0,1,8 is correct
R A H U L
Join the discussion

by Brent@GMATPrepNow » Fri Sep 20, 2013 6:02 am
faraz_jeddah wrote:If the terms of a sequence t1, t2, ....tn, what is the value of n?
1. The sum of the n terms is 3,124
2. The average (arithmetic mean) of the n terms is 4
For those of you who attempted the original question, here's one approach.

Target question: What is the value of n?

Statement 1: The sum of the n terms is 3,124
There are several sequences that satisfy this condition. Here are two:
Case a: the sequence is {0, 3124}, in which case n = 2
Case b: the sequence is {0, 0, 3124}, in which case n = 3
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: The average (arithmetic mean) of the n terms is 4
There are several sequences that satisfy this condition. Here are two:
Case a: the sequence is {4, 4}, in which case n = 2
Case b: the sequence is {4, 4, 4}, in which case n = 3
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
We know: average = (sum of n numbers)/n
Statement 1 tells us the sum, and statement 2 tells us the average.
So, we get: 4 = 3124/n (which we COULD solve for n)
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Join the discussion