It is currently 17 Jan 2018, 22:17

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If sequence S has 120 terms, what is the 105th term of S?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

1 KUDOS received
Director
Director
User avatar
Joined: 10 Mar 2013
Posts: 588

Kudos [?]: 511 [1], given: 200

Location: Germany
Concentration: Finance, Entrepreneurship
GMAT 1: 580 Q46 V24
GPA: 3.88
WE: Information Technology (Consulting)
GMAT ToolKit User
If sequence S has 120 terms, what is the 105th term of S? [#permalink]

Show Tags

New post 19 Sep 2015, 12:01
1
This post received
KUDOS
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

91% (00:26) correct 9% (00:25) wrong based on 723 sessions

HideShow timer Statistics

If sequence S has 120 terms, what is the 105th term of S?

(1) The first term of S is −8.
(2) Each term of S after the first term is 10 more than the preceding term.

Source: [OG 2016]
[Reveal] Spoiler: OA

_________________

When you’re up, your friends know who you are. When you’re down, you know who your friends are.

Share some Kudos, if my posts help you. Thank you !

800Score ONLY QUANT CAT1 51, CAT2 50, CAT3 50
GMAT PREP 670
MGMAT CAT 630
KAPLAN CAT 660


Last edited by ENGRTOMBA2018 on 19 Sep 2015, 13:27, edited 1 time in total.
Edited the question and renamed the topic

Kudos [?]: 511 [1], given: 200

1 KUDOS received
Current Student
avatar
S
Joined: 20 Mar 2014
Posts: 2685

Kudos [?]: 1845 [1], given: 800

Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge
Re: If sequence S has 120 terms, what is the 105th term of S? [#permalink]

Show Tags

New post 19 Sep 2015, 13:35
1
This post received
KUDOS
2
This post was
BOOKMARKED
BrainLab wrote:
If sequence S has 120 terms, what is the 105th term of S?

(1) The first term of S is −8.
(2) Each term of S after the first term is 10 more than the preceding term.

Source: [OG 2016]


Follow the posting guidelines. If a question is from a particular source or year of official guide, mention it in the question and not in the topic title.

Note that nowhere in the original question is it mentioned that the sequence S is some kind of a particular sequence (Arithmetic, Geometric etc). 105th term= \(S_{105}\)

Per statement 1, a=first term =-8. Still do not know what kind of a sequence is this.

Per statement 2, Given that the sequence is an arithmetic progression (difference between 2 consecutive terms is constant) \(a_n\)=nth term in the sequence = \(a+(n-1)*d\) where n=105 and d =10. Thus, 105th term = a+(105-1)*10 = a+1040. Still no information on 'a' or the first term. Not sufficient.

Combining the 2 statements, a=-8 and thus, \(S_{105}\) = \(a+(n-1)*d\) = -108+1040=932. C is thus the correct answer.

Kudos [?]: 1845 [1], given: 800

2 KUDOS received
Senior Manager
Senior Manager
User avatar
G
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 479

Kudos [?]: 583 [2], given: 63

Location: United States (CA)
Age: 38
GMAT 1: 770 Q47 V48
GMAT 2: 730 Q44 V47
GMAT 3: 750 Q50 V42
GRE 1: 337 Q168 V169
WE: Education (Education)
Re: If sequence S has 120 terms, what is the 105th term of S? [#permalink]

Show Tags

New post 27 Mar 2016, 19:25
2
This post received
KUDOS
Here is a visual that should help.
Attachments

Screen Shot 2016-03-27 at 8.24.16 PM.png
Screen Shot 2016-03-27 at 8.24.16 PM.png [ 316.93 KiB | Viewed 5621 times ]


_________________

Harvard grad and 770 GMAT scorer, offering high-quality private GMAT tutoring, both in-person and online via Skype, since 2002.

GMAT Action Plan - McElroy Tutoring

Kudos [?]: 583 [2], given: 63

Expert Post
Top Contributor
SVP
SVP
User avatar
P
Joined: 11 Sep 2015
Posts: 1983

Kudos [?]: 2864 [0], given: 364

Location: Canada
If sequence S has 120 terms, what is the 105th term of S? [#permalink]

Show Tags

New post 24 Jul 2017, 09:50
Expert's post
Top Contributor
BrainLab wrote:
If sequence S has 120 terms, what is the 105th term of S?

(1) The first term of S is −8.
(2) Each term of S after the first term is 10 more than the preceding term.

Source: [OG 2016]


Target question: What is the 105th term of S?

Given: Sequence S has 120 terms

Statement 1: The first term of S is −8.
We have no information about the nature of the sequence.
So, knowing the value of term 1 won't help is determine the value of term 105
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: Each term of S after the first term is 10 more than the preceding term.
This statement provides information about the nature of the sequence, but we don't know the first term.
For example, the 105th term of the sequence {10, 20, 30, 40, ....} will be different from the 105th term of the sequence {3310, 3320, 3330, 3340, ....}
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that term 1 = -8
Statement 2 tells us that every term (after term 1) is 10 more than the preceding term
So, the sequence is as follows: -8, 2, 12, 22, 32, 42, 52, 62, .....
At this point we COULD determine the value of the 105th term of the sequence . For example, we could keep listing every term until we get to the 105th term. However, we don't need to do that, since our sole objective is to determine whether we have sufficient information to answer the target question (which we DO)
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer:
[Reveal] Spoiler:
C


RELATED VIDEO

_________________

Brent Hanneson – Founder of gmatprepnow.com

Image

Kudos [?]: 2864 [0], given: 364

Expert Post
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10696

Kudos [?]: 3775 [0], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: If sequence S has 120 terms, what is the 105th term of S? [#permalink]

Show Tags

New post 16 Dec 2017, 14:13
Hi All,

This question is another great example of a 'concept' question - if you understand the concept(s) involved, then you can get to the correct answer without doing much (if any) math.

We're told that a sequence has 120 terms. We're asked for the 105th term in the sequence.

1) The first term of S is -8.

While this Fact tells us the 1st term in the sequence, it does NOT tell us how the sequence progresses. The sequence might increase, decrease or 'oscillate', so there's no way to determine the 105th term.
Fact 1 is INSUFFICIENT.

2) Each term of S after the first term is 10 more than the preceding term.

Fact 2 tells us how the sequence progresses (each term is 10 greater than the term that precedes it), BUT we don't know any of the individual terms, so there's no way to determine the exact value of any of them.
Fact 2 is INSUFFICIENT.

Combined, we know:
-The first term is -8
-Each term is 10 greater than the one that precedes it.

Thus, we could figure out the 105th term (either algebraically or y just "adding 10s" until we get to that term). Either way, we CAN determine the value of the 105th term.
Combined, SUFFICIENT.

Final Answer:
[Reveal] Spoiler:
C


GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3775 [0], given: 173

Re: If sequence S has 120 terms, what is the 105th term of S?   [#permalink] 16 Dec 2017, 14:13
Display posts from previous: Sort by

If sequence S has 120 terms, what is the 105th term of S?

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


cron

GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.