November 20, 2018 November 20, 2018 09:00 AM PST 10:00 AM PST The reward for signing up with the registration form and attending the chat is: 6 free examPAL quizzes to practice your new skills after the chat. November 20, 2018 November 20, 2018 06:00 PM EST 07:00 PM EST What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.
Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 30 Nov 2010
Posts: 222
Schools: UC Berkley, UCLA

In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
15 Feb 2011, 07:28
Question Stats:
74% (01:00) correct 26% (01:03) wrong based on 538 sessions
HideShow timer Statistics
In a sequence of terms in which each term is three times the previous term, what is the fourth term? (1) The first term is 3. (2) The secondtolast term is 3^10.
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Thank you for your kudoses Everyone!!!
"It always seems impossible until its done." Nelson Mandela




Math Expert
Joined: 02 Sep 2009
Posts: 50627

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
15 Feb 2011, 07:35
mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. In a sequence of terms in which each term is three times the previous term, what is the fourth term?(1) The first term is 3 > sequence is: 3, 9, 27, 81, ... so the fourth term is 81. Sufficient. (2) The secondtolast term is 3^10 > since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. Answer: A.
_________________
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




Manager
Joined: 30 Nov 2010
Posts: 222
Schools: UC Berkley, UCLA

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
15 Feb 2011, 07:59
Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. In a sequence of terms in which each term is three times the previous term, what is the fourth term?(1) The first term is 3 > sequence is: 3, 9, 27, 81, ... so the fourth term is 81. Sufficient. (2) The secondtolast term is 3^10 > since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. Answer: A. I had to think about that for a bit before I could sincerely agree with you, Bunuel. Thanks!
_________________
Thank you for your kudoses Everyone!!!
"It always seems impossible until its done." Nelson Mandela



Intern
Joined: 26 Jul 2010
Posts: 34
Schools: Haas, HBS, UNC, Duke, Kellogg, etc
WE 1: Investment Banking Domain, FunctionallyTechnology

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
15 Feb 2011, 10:03
Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. In a sequence of terms in which each term is three times the previous term, what is the fourth term?(1) The first term is 3 > sequence is: 3, 9, 27, 81, ... so the fourth term is 81. Sufficient. (2) The secondtolast term is 3^10 > since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. Answer: A. You are truly awesome .. with DS.... i kinda assumed it to be 2nd term when said 2nd to last assuming that there r only 4 terms...thanks bunuel...



Manager
Joined: 04 Dec 2009
Posts: 55
Location: INDIA

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
05 Mar 2011, 20:57
Ans : a , in second statment we dont know where serise start it can start from any no so insuff.
_________________
MBA (Mind , Body and Attitude )



Director
Joined: 01 Feb 2011
Posts: 664

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
06 Mar 2011, 12:18
Good question.
First one is sufficient, as we have the rate at which each term is changing and first term which are enough to calculate what is neeed.
Second one is not sufficient , because we dont know the starting term and no of terms.
Hence A is the answer.



Manager
Joined: 23 Oct 2011
Posts: 82

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
13 Jan 2012, 15:39
Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. regarding the second statement. Someone could interpret the secondtolast term as the ratio between the second and the last term. Since we know that it is an exponential expression dividing the second with the last term should result a fraction smaller than 1. Therefore, someone could assume that the second statement is wrong. is my reasoning valid?



Math Expert
Joined: 02 Sep 2009
Posts: 50627

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
16 Jan 2012, 16:24
SonyGmat wrote: Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. regarding the second statement. Someone could interpret the secondtolast term as the ratio between the second and the last term. Since we know that it is an exponential expression dividing the second with the last term should result a fraction smaller than 1. Therefore, someone could assume that the second statement is wrong. is my reasoning valid? Responding to a pm. If it were the case it would have been something like "the ratio of second to last term is ..." Also on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other. So if on the GMAT your interpretation of the statements leads you to conclude that the statements are impossible/incorrect or contradict each other then the case would be that your interpretation is wrong not the statements.
_________________
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



Intern
Joined: 23 May 2011
Posts: 3

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
09 Jul 2012, 01:54
thanks brunel for pointing out.. you are a jem



Intern
Joined: 29 Nov 2015
Posts: 13

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
14 Jan 2016, 11:06
Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. In a sequence of terms in which each term is three times the previous term, what is the fourth term?(1) The first term is 3 > sequence is: 3, 9, 27, 81, ... so the fourth term is 81. Sufficient. (2) The secondtolast term is 3^10 > since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. Answer: A. Hi Bunuel, since the question states that each term is 3 times another term, it means that for the nth term, the value will be 3^n. So I assumed that the 10th term is 3^10, last term is 3^11 and 4th term is 3^4. What was the flaw in my logic? Thanks in advance.



CEO
Joined: 20 Mar 2014
Posts: 2635
Concentration: Finance, Strategy
GPA: 3.7
WE: Engineering (Aerospace and Defense)

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
14 Jan 2016, 11:14
sarathvr wrote:
Hi Bunuel, since the question states that each term is 3 times another term, it means that for the nth term, the value will be 3^n. So I assumed that the 10th term is 3^10, last term is 3^11 and 4th term is 3^4. What was the flaw in my logic? Thanks in advance. You are not interpreting the text in red above correctly. When you say "3 times the other term", it means that if the 1st term is a, then the 2nd term is 3a, 3rd term is 3a*3=9a etc. Thus the sequence becomes a,3a,9a,27a .... and NOT 3^n as you have mentioned. This is where you are making a mistake. Hope this helps.



Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6517
GPA: 3.82

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
14 Jan 2016, 17:23
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution. In a sequence of terms in which each term is three times the previous term, what is the fourth term? (1) The first term is 3. (2) The secondtolast term is 3^10. Modify the original condition and the question and suppose the sequence A_n. Then it becomes A_(n+1)=3A_(n) and once you figure out A_(1), you can figure out everything. So there is 1 variable, which should match with the number of equations. So you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer. For 1), A_(1)=3 > A_(2)=3^2, A_(3)=3^3, A_(4)=3^4, which is unique and sufficient. For 2), you can’t figure out where the last term comes, which is not sufficient. Therefore, the answer is A. For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The oneandonly World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only $99 for 3 month Online Course" "Free Resources30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons  try it yourself"



Intern
Joined: 01 Jan 2016
Posts: 21

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
23 Sep 2016, 20:23
Why is B incorrect? Is it because having the "last term" does not specify a finite value from which we can compute the "last  1, last 2, ..., 4th" term?



Senior Manager
Status: Come! Fall in Love with Learning!
Joined: 05 Jan 2017
Posts: 495
Location: India

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
23 Feb 2017, 04:49
Prompt analysis A geometric progression following the sequence tn = a. r^(n1). r= 3 Superset The answer will be any real number. Translation In order to find t4, we need a and r or any two equation to solve for a and r. Statement analysis St 1: a =3. r =3. There fore t4 = 3. 3^3 = 81. ANSWER St 2: ar/ar^(n1)= 3^10. We don't have any idea about a. INSUFFICIENT. Option A
_________________
GMAT Mentors



Manager
Joined: 23 Dec 2013
Posts: 159
Location: United States (CA)
GMAT 1: 710 Q45 V41 GMAT 2: 760 Q49 V44
GPA: 3.76

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
28 May 2017, 19:37
mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. The goal is to find the fourth term in this sequence. We need to know the first term and the pattern between each term to determine the value of the fourth term. Statement 1) x = 3 = first term 9 = second term 27 = third term 81 = fourth term Sufficient. Statement 2) The second to last term is 3^10. If there are four total terms, then the value of the fourth term is 3^11. If there are six total terms, then the value of the fourth term is 3^9. Insufficient.



Senior Manager
Joined: 15 Jan 2017
Posts: 359

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
02 Oct 2017, 12:17
St 1: quite clear. T1= 3, T2 = 9, T3 = 27, T4 = 81, SUFF St2: SECOND last term is 3*10. Last would be 9*10. But what would be the first term? We don't know for sure sure if its 10 or some fraction, because we are multiplying 3 into something, so it should already be a multiple of 3. So NOT SUFF.
Ans A



Intern
Joined: 28 Sep 2017
Posts: 4
WE: Business Development (NonProfit and Government)

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
10 Oct 2017, 03:44
Quite easy.
3, 9, 27 and 81.
Second data point has no bearing on what's been asked of us.



Target Test Prep Representative
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
12 Oct 2017, 17:17
mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10. The first term is 3. Our terms are as follows: 3, 9, 27, 81… So, the fourth term is 81. Statement one alone is sufficient to answer the question. Statement Two Alone: The secondtolast term is 3^10. Since we do not know the number of terms in the set, statement two alone is not sufficient to answer the question. For example, if there are 4 terms in the set, the fourth term is 3^11. However, if there are 5 terms in the set, the fourth term is 3^10. Answer: A
_________________
Jeffery Miller
Head of GMAT Instruction
GMAT Quant SelfStudy Course
500+ lessons 3000+ practice problems 800+ HD solutions



Manager
Joined: 19 Aug 2016
Posts: 86

In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
11 Nov 2017, 03:24
Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. In a sequence of terms in which each term is three times the previous term, what is the fourth term?(1) The first term is 3 > sequence is: 3, 9, 27, 81, ... so the fourth term is 81. Sufficient. (2) The secondtolast term is 3^10 > since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. Answer: A. Hi Bunuel Can u pls explain The secondtolast term is 3^10> since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. what is the meaning of second to last term? I thought it means the last but second term, which means the 3rd term



Math Expert
Joined: 02 Sep 2009
Posts: 50627

Re: In a sequence of terms in which each term is three times the
[#permalink]
Show Tags
11 Nov 2017, 04:05
zanaik89 wrote: Bunuel wrote: mariyea wrote: In a sequence of terms in which each term is three times the previous term, what is the fourth term?
(1) The first term is 3.
(2) The secondtolast term is 3^10.
I think the ans should be D. But OA is different. In a sequence of terms in which each term is three times the previous term, what is the fourth term?(1) The first term is 3 > sequence is: 3, 9, 27, 81, ... so the fourth term is 81. Sufficient. (2) The secondtolast term is 3^10 > since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. Answer: A. Hi Bunuel Can u pls explain The secondtolast term is 3^10> since we don't know how many terms are there in the sequence then we don't know which term is secondtolast. For example: if it's third term then fourth (and last) will be 3^11, if it's fifth term then the fourth term is 3^9, ... Not sufficient. what is the meaning of second to last term? I thought it means the last but second term, which means the 3rd term The secondtolast term means the term before the last term.
_________________
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




Re: In a sequence of terms in which each term is three times the &nbs
[#permalink]
11 Nov 2017, 04:05






