Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 44421

The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
30 Jan 2014, 01:50
1
This post received KUDOS
Expert's post
4
This post was BOOKMARKED
Question Stats:
89% (00:58) correct 11% (01:03) wrong based on 705 sessions
HideShow timer Statistics
The Official Guide For GMAT® Quantitative Review, 2ND EditionThe sequence \(a_1\), \(a_2\), \(a_3\), \(a_4\), \(a_5\) is such that \(a_n= a_{n1} + 5\) for \(2\leq n \leq 5\). If \(a_5 = 31\), what is the value of \(a_1\) ? (A) 1 (B) 6 (C) 11 (D) 16 (E) 21 Problem Solving Question: 67 Category: Algebra Sequences Page: 70 Difficulty: 600 GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition  Quantitative Questions ProjectEach week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution. We'll be glad if you participate in development of this project: 1. Please provide your solutions to the questions; 2. Please vote for the best solutions by pressing Kudos button; 3. Please vote for the questions themselves by pressing Kudos button; 4. Please share your views on difficulty level of the questions, so that we have most precise evaluation. Thank you!
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Math Expert
Joined: 02 Sep 2009
Posts: 44421

The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
30 Jan 2014, 01:50



Director
Joined: 25 Apr 2012
Posts: 720
Location: India
GPA: 3.21
WE: Business Development (Other)

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
30 Jan 2014, 03:10
1
This post received KUDOS
1
This post was BOOKMARKED
The sequence \(a_1\), \(a_2\), \(a_3\), \(a_4\), \(a_5\) is such that \(a_n= a_{n1} + 5\) for \(2\leq n \leq 5\). If \(a_5 = 31\), what is the value of \(a_1\) ? (A) 1 (B) 6 (C) 11 (D) 16 (E) 21 Sol: Given a5=31....and also a5=a4+5 > a4=26> a3=21>a2=16 >a1=11. Ans C 600 level is okay
_________________
“If you can't fly then run, if you can't run then walk, if you can't walk then crawl, but whatever you do you have to keep moving forward.”



Senior Manager
Joined: 20 Dec 2013
Posts: 266
Location: India

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
30 Jan 2014, 03:31
1
This post received KUDOS
Ans.C This is nothing but an AP with common diff=5 a5=31, a4=26 a3=21, a2=16, a1=11
a5=a1+4d 31=a1+4*5 3120=a1=11



Manager
Joined: 18 Oct 2013
Posts: 81
Location: India
Concentration: Technology, Finance
Schools: Duke '16, Johnson '16, Kelley '16, Tepper '16, Marshall '16, McDonough '16, Insead '14, HKUST '16, HSG '15, Schulich '15, Erasmus '16, IE April'15, Neeley '15
GMAT 1: 580 Q48 V21 GMAT 2: 530 Q49 V13 GMAT 3: 590 Q49 V21
WE: Information Technology (Computer Software)

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
30 Jan 2014, 10:42
1
This post received KUDOS
2
This post was BOOKMARKED
This answer can be easily be solve by A.P. The sequence is an A.P. with each term at an increment of 5 from the previous term. So a5 is nothing but a1+20.
a5=a1+20=31 => a1=11.
Answer is C



Manager
Joined: 04 Oct 2013
Posts: 161
Location: India
GMAT Date: 05232015
GPA: 3.45

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
31 Jan 2014, 06:13
1
This post received KUDOS
2
This post was BOOKMARKED
The sequence \(a_1, a_2, a_3, a_4, a_5\) is such that \(a_n= a_{n1} + 5\) for \(2\leq n \leq 5\). If \(a_5 = 31\), what is the value of \(a_1\) ?
(A) 1 (B) 6 (C) 11 (D) 16 (E) 21
Given sequence is A.P. with common difference of 5. Last Term  First Term = (Number of terms 1)* common difference
\(a_5a_1 = (51)*\) \(common\) \(difference\)
Or, \(31a_1=(51)*5\)
Or, \(a_1=3120=11\)
Answer: (C)



Intern
Joined: 21 Oct 2012
Posts: 36
Location: United States
Concentration: Marketing, Operations
GMAT 1: 650 Q44 V35 GMAT 2: 600 Q47 V26 GMAT 3: 660 Q43 V38
GPA: 3.6
WE: Information Technology (Computer Software)

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
18 Mar 2014, 23:12
Bunuel wrote: SOLUTION
The sequence \(a_1\), \(a_2\), \(a_3\), \(a_4\), \(a_5\) is such that \(a_n= a_{n1} + 5\) for \(2\leq n \leq 5\). If \(a_5 = 31\), what is the value of \(a_1\) ?
(A) 1 (B) 6 (C) 11 (D) 16 (E) 21
\(a_5 = 31\); \(a_4 =315=26\); \(a_3 =265=21\); \(a_2 =215=16\); \(a_1 =165=1\).
Answer: C. But 2<= n <= 5 so how is this applicable to a1 i.e. n=1?



Math Expert
Joined: 02 Sep 2009
Posts: 44421

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
19 Mar 2014, 01:59



Director
Joined: 10 Mar 2013
Posts: 578
Location: Germany
Concentration: Finance, Entrepreneurship
GPA: 3.88
WE: Information Technology (Consulting)

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
14 May 2015, 15:25
5 is constant here so > a5  4*5 = 11 (4*5 because we have 4 numbers between a5 and a1 ... a4,3,2,1 )
_________________
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



Director
Joined: 24 Nov 2015
Posts: 582
Location: United States (LA)

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
04 May 2016, 03:40
a5 = 31 a4 = 315 = 26 a3 = 26  5 = 21 a2 = 21  5 = 16 a1 = 16  5 = 11 correct answer  C



NonHuman User
Joined: 09 Sep 2013
Posts: 6545

Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for [#permalink]
Show Tags
23 Mar 2018, 06:08
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: The sequence a1, a2, a3, a4, a5 is such that an=a(n1)+5 for
[#permalink]
23 Mar 2018, 06:08






