GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 07 Dec 2019, 12:41 ### 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

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.  # What is the 1st term in sequence S ?

Author Message
TAGS:

### Hide Tags

Senior Manager  Joined: 23 Aug 2003
Posts: 398
Location: In the middle of nowhere
What is the 1st term in sequence S ?  [#permalink]

### Show Tags

1
1 00:00

Difficulty:   5% (low)

Question Stats: 87% (00:49) correct 13% (00:50) wrong based on 403 sessions

### HideShow timer Statistics

What is the 1st term in sequence S ?

(1) The 3rd term in S is 2.
(2) The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd.

Project DS Butler: Day 1: Data Sufficiency (DS1)

Magoosh GMAT Instructor G
Joined: 28 Dec 2011
Posts: 4471
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

2
vikasp99 wrote:
What is the 1st term in sequence S?

(1) The 3rd term of S is 4.
(2) The 2nd term of S is three times the 1st, and the 3rd term is four times
the 2nd.

Dear vikasp99,

I'm happy to help. This is a poorly written question. It actually has nothing to do with sequences per se. It would be much better if the question simply discussed three separate variables. It's also not very hard. It's just not a good question.

Each statement individual is insufficient.

Combined:
a3 = 4 = 4*(a2)
therefore
a2 = 1

a2 = 1 = 3*(a1)
therefore
a1 = 1/3

Numerical answer. Combined statements are sufficient. Poor question.

OA = (C)

Does all this make sense?
Mike _________________
Mike McGarry
Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)
NUS School Moderator V
Joined: 18 Jul 2018
Posts: 1024
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

2
1
1
Question stem. What's the value of $$S_1$$ ?

From statement 1:

$$S_3 = 2$$.
Clearly Insufficient.

From statement 2:

$$S_2 = 2S_1$$
$$S_3 = 3S_2$$
All 3 unknows.
Insufficient.

Combining both:

$$S_3 = 2$$
Then $$S_2$$ = 1.
So, $$S_1$$ = 1/2.

RC Moderator V
Joined: 24 Aug 2016
Posts: 780
GMAT 1: 540 Q49 V16 GMAT 2: 680 Q49 V33 Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

1
(1) The 3rd term in S is 2. - NS: S3 =2
(2) The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd. -NS : ==> S3 =3S2 =6S1
(1+2) Sufficient : as S3 =2 , Hence, S1 = $$\frac{2}{6} = \frac{1}{3}$$ ..... Hence Ans C
_________________
Please let me know if I am going in wrong direction.
Thanks in appreciation.
Manager  P
Joined: 09 Jun 2018
Posts: 185
Location: United States
GPA: 3.95
WE: Manufacturing and Production (Energy and Utilities)
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

1
No need to solve completely as this is a DS question!

Stmt 1: S3 = 2, No info on S1, Insufficient. Eliminate A,D
Stmt 2: S2 = 2*S1, S3 = 3*S2, No values given for any term, so cannot find out value of S1, Insufficient. Eliminate B

Combined: We can find the value of S1, by back tracking through the three equations from Stmts 1 and 2. Hence Sufficient.

Option C
Senior Manager  D
Joined: 05 Jul 2018
Posts: 462
Location: India
Concentration: General Management, Technology
GMAT 1: 600 Q47 V26 GRE 1: Q162 V149 GPA: 3.6
WE: Information Technology (Consulting)
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

1
gmatbusters wrote:

Project DS Butler: Day 1: Data Sufficiency (DS1)

What is the 1st term in sequence S ?
(1) The 3rd term in S is 2.
(2) The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd.

Statement 1 This only gives us the value of 3rd term and no relation whatsoever to the 1st term of the sequence. There is no way we can find the first term of the sequence using this info. Hence, this is INSUFFICIENT

Statement 2 This gives us relation about the 3 terms. Now we know the first 3 terms will look somewhat like this--> a, 2a, 6a. But we have no clue about the value of 'a' here. Hence, this alone is INSUFFICIENT

Statement 1 + Statement 2 Now we know that 6a=2. Hence we can find the value of a which is 1/3. hence we get a unique numerical value. hence this is SUFFICIENT

NUS School Moderator V
Joined: 18 Jul 2018
Posts: 1024
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

1
gzuz wrote:
gmatbusters wrote:

Project DS Butler: Day 1: Data Sufficiency (DS1)

What is the 1st term in sequence S ?
(1) The 3rd term in S is 2.
(2) The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd.

Hello gmatbusters,

in the question is not said, that there are only 3 terms.
Do I have to assume so?

I thought it would be E because there was no information about the total number of terms

Hey gzuz, Let me try to answer. The minimum number of terms you need to determine the kind of series (AP, GP or HP).
Hence when 2 statements are combined, we are able the find the first term.
GMAT Club Legend  V
Joined: 12 Sep 2015
Posts: 4125
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

1
Top Contributor
gzuz wrote:
Hello gmatbusters,

in the question is not said, that there are only 3 terms.
Do I have to assume so?

I thought it would be E because there was no information about the total number of terms

The target question only asks us to determine "the 1st term in sequence S"
So, the total number of terms in the sequence has no bearing on our ability to answer the target question.

Cheers,
Brent
_________________
Director  S
Status: Come! Fall in Love with Learning!
Joined: 05 Jan 2017
Posts: 526
Location: India
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

Let the number of the sequence be a,b,c,d....
Statement 1: c = 4. no idea about a. INSUFFICIENT
Statement 2: b=3a and c = 4b = 12a. no data about a. INSUFFICIENT

St 1 &St 2: c = 4 = 12a or a = 1/3. ANSWER

Option C
_________________
GMAT Mentors Director  G
Joined: 19 Oct 2013
Posts: 511
Location: Kuwait
GPA: 3.2
WE: Engineering (Real Estate)
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

Given that $$S_3 = 2$$. We cannot figure any specific value for S1

Insufficient.

We look at Statement 2) it tells us$$S_2 = 2*S_1$$ and $$S_3 = 3*S_2$$.

Still insufficient as I have 2 equations and 3 variables.

Combining both we have one variable that can be substituted to provide a numerical value. This numerical value can then be substituted in the other equation.

C
GMAT Club Legend  V
Joined: 12 Sep 2015
Posts: 4125
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

Top Contributor
gmatbusters wrote:

Project DS Butler: Day 1: Data Sufficiency (DS1)

What is the 1st term in sequence S ?
(1) The 3rd term in S is 2.
(2) The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd.

Target question: What is the 1st term in sequence S ?

Statement 1: The 3rd term in S is 2
Since we're not given any information about the NATURE of the sequence, there's no way to answer the target question with certainty.
So, statement 1 is NOT SUFFICIENT

Statement 2: The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd.
Great, we're given information about the NATURE of the sequence, but we aren't given the VALUE of any terms.
For example, consider these two possible cases that satisfy statement 2:
Case a: The first 3 terms are: {1, 2, 6....}. In this case, the answer to the target question is the 1st term is 1
Case b: The first 3 terms are: {3, 6, 18....}. In this case, the answer to the target question is the 1st term is 3
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that the 3rd term in S is 2
Statement 2 tells us that the 3rd term is three times the 2nd. So, if the 3rd term is 2, then the 2nd term must be 2/3
Statement 2 also tells us that the 2nd term in S is twice the 1st. So, if the 2nd term is 2/3, then the 1st term must be 1/3
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Cheers,
Brent
_________________
Intern  B
Joined: 17 Dec 2018
Posts: 7
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

gmatbusters wrote:

Project DS Butler: Day 1: Data Sufficiency (DS1)

What is the 1st term in sequence S ?
(1) The 3rd term in S is 2.
(2) The 2nd term in S is twice the 1st, and the 3rd term is three times the 2nd.

Hello gmatbusters,

in the question is not said, that there are only 3 terms.
Do I have to assume so?

I thought it would be E because there was no information about the total number of terms
Non-Human User Joined: 09 Sep 2013
Posts: 13724
Re: What is the 1st term in sequence S ?  [#permalink]

### Show Tags

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.
_________________ Re: What is the 1st term in sequence S ?   [#permalink] 11 Jul 2019, 00:04
Display posts from previous: Sort by

# What is the 1st term in sequence S ?  