Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t : GMAT Problem Solving (PS)
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 10 Dec 2016, 03:07

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t

Author Message
TAGS:

### Hide Tags

VP
Status: Far, far away!
Joined: 02 Sep 2012
Posts: 1123
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8
Followers: 180

Kudos [?]: 1914 [3] , given: 219

Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t [#permalink]

### Show Tags

12 Apr 2013, 00:10
3
KUDOS
3
This post was
BOOKMARKED
00:00

Difficulty:

45% (medium)

Question Stats:

67% (02:18) correct 33% (01:46) wrong based on 153 sessions

### HideShow timer Statistics

Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such that A has an even number of terms. If the sum of terms at odd positions is p and sum of terms at even positions is q, what is the ratio of p to q (take the common ratio as r)?

(A) r
(B) r2
(C) 1/r2
(D) 1/r
(E) None of these
[Reveal] Spoiler: OA

_________________

It is beyond a doubt that all our knowledge that begins with experience.

Kant , Critique of Pure Reason

Tips and tricks: Inequalities , Mixture | Review: MGMAT workshop
Strategy: SmartGMAT v1.0 | Questions: Verbal challenge SC I-II- CR New SC set out !! , My Quant

Rules for Posting in the Verbal Forum - Rules for Posting in the Quant Forum[/size][/color][/b]

Intern
Joined: 15 Oct 2012
Posts: 25
Followers: 0

Kudos [?]: 13 [0], given: 1

Re: Latest Grail question bank PS 700 level [#permalink]

### Show Tags

12 Apr 2013, 00:37
i guess GP over here means Geometric Progression....
MBA Section Director
Affiliations: GMAT Club
Joined: 21 Feb 2012
Posts: 3723
Location: India
City: Pune
GMAT 1: 680 Q49 V34
GPA: 3.4
Followers: 379

Kudos [?]: 2783 [4] , given: 1961

Re: Latest Grail question bank PS 700 level [#permalink]

### Show Tags

12 Apr 2013, 00:49
4
KUDOS
Expert's post
I think it should be 1/r

Let A be the GP with first term as a , common ratio as r, and number of terms as 6

GP = a, ar, ar^2, ar^3, ar^4, ar^5

Sum of GP = $$\frac{a (r^n - 1)}{r-1}$$ where a=first term, n=number of terms, r=common ratio

Odd GP = a, ar^2, ar^4 Sum odd GP = $$\frac{a (r^6 - 1)}{r^2-1}$$

Even GP = ar, ar^3, ar^5 Sum even GP = $$\frac{ar (r^6 - 1)}{r^2-1}$$

Desired Ratio = $$\frac{a}{ar}$$ = $$\frac{1}{r}$$

PS :- G.P. means Geometric Progression
_________________
Current Student
Joined: 04 Mar 2013
Posts: 69
Location: India
Concentration: Strategy, Operations
Schools: Booth '17 (M)
GMAT 1: 770 Q50 V44
GPA: 3.66
WE: Operations (Manufacturing)
Followers: 5

Kudos [?]: 52 [1] , given: 27

Re: Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such [#permalink]

### Show Tags

12 Apr 2013, 03:56
1
KUDOS
You dont need to know the formula for the Sum of GP to solve this

Just write the odd and even digits of the given statement together

P would become a +ar^2 + ar^4

Q would become ar + ar^3 + ar^5

=> P/Q = a(1 + r^2 + r^4) / ar (1 + r^2 + r^4)
=> P/Q = a(1 + r^2 + r^4) / ar(1 + r^2 + r^4)
=> P/Q = a/ar
=> P/Q = 1/r
_________________

When you feel like giving up, remember why you held on for so long in the first place.

Manager
Status: Do till 740 :)
Joined: 13 Jun 2011
Posts: 113
Concentration: Strategy, General Management
GMAT 1: 460 Q35 V20
GPA: 3.6
WE: Consulting (Computer Software)
Followers: 1

Kudos [?]: 8 [0], given: 19

Re: Latest Grail question bank PS 700 level [#permalink]

### Show Tags

27 Oct 2013, 16:01
Narenn wrote:
I think it should be 1/r

Let A be the GP with first term as a , common ratio as r, and number of terms as 6

GP = a, ar, ar^2, ar^3, ar^4, ar^5

Sum of GP = $$\frac{a (r^n - 1)}{r-1}$$ where a=first term, n=number of terms, r=common ratio

Odd GP = a, ar^2, ar^4 Sum odd GP = $$\frac{a (r^6 - 1)}{r^2-1}$$

Even GP = ar, ar^3, ar^5 Sum even GP = $$\frac{ar (r^6 - 1)}{r^2-1}$$

Desired Ratio = $$\frac{a}{ar}$$ = $$\frac{1}{r}$$

PS :- G.P. means Geometric Progression

Hi, how can the number of terms be 6. It must be 3 right? Since for the even and odd terms it is just 3. Is that correct?

Thanks
Manager
Joined: 29 Sep 2013
Posts: 53
Followers: 0

Kudos [?]: 33 [0], given: 48

Re: Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t [#permalink]

### Show Tags

03 Nov 2013, 17:15
Zarrolou wrote:
Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such that A has an even number of terms. If the sum of terms at odd positions is p and sum of terms at even positions is q, what is the ratio of p to q (take the common ratio as r)?

(A) r
(B) r2
(C) 1/r2
(D) 1/r
(E) None of these

If A = ($$a, ar, ar^2, ar^4,$$…), then shouldn't the next terms be $$ar^8$$ and $$ar^16$$. or am I missing something.
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 12905
Followers: 563

Kudos [?]: 158 [0], given: 0

Re: Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t [#permalink]

### Show Tags

04 Sep 2015, 10:34
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.
_________________
Manager
Joined: 23 Sep 2015
Posts: 95
Concentration: General Management, Finance
GMAT 1: 680 Q46 V38
GMAT 2: 690 Q47 V38
GPA: 3.5
Followers: 0

Kudos [?]: 13 [0], given: 213

Re: Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t [#permalink]

### Show Tags

06 Nov 2015, 20:34
Narenn wrote:
I think it should be 1/r

Let A be the GP with first term as a , common ratio as r, and number of terms as 6

GP = a, ar, ar^2, ar^3, ar^4, ar^5

Sum of GP = $$\frac{a (r^n - 1)}{r-1}$$ where a=first term, n=number of terms, r=common ratio

Odd GP = a, ar^2, ar^4 Sum odd GP = $$\frac{a (r^6 - 1)}{r^2-1}$$

Even GP = ar, ar^3, ar^5 Sum even GP = $$\frac{ar (r^6 - 1)}{r^2-1}$$

Desired Ratio = $$\frac{a}{ar}$$ = $$\frac{1}{r}$$

PS :- G.P. means Geometric Progression

how did the denominator change from r-1 to r^2-1 ?
Intern
Joined: 12 Jun 2011
Posts: 2
GMAT 1: 690 Q49 V35
Followers: 0

Kudos [?]: 5 [0], given: 27

Re: Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t [#permalink]

### Show Tags

14 Dec 2015, 20:17
A = {a, ar, ar2, ar4,…..} <--- This is not a GP.
A = {a, ar, ar2, ar3,…..} <--- This is.
Re: Let A be a G.P. defined by A = {a, ar, ar2, ar4,…..}, such t   [#permalink] 14 Dec 2015, 20:17
Similar topics Replies Last post
Similar
Topics:
Let function be defined as follows: (x)=x!+(x+1)!/(x+2)!. What is t 2 30 Nov 2016, 01:50
2 If the ratio of the sum of the first 6 terms of a G.P. to the sum of 3 14 Feb 2016, 04:38
Let C be defined as the sum of all prime numbers between 0 and 30. 5 08 Nov 2015, 23:27
7 Let n~ be defined for all positive integers n as the remainder when (n 2 05 Nov 2015, 04:57
6 Let f(x,y) be defined as the remainder when (x–y)! is divided by x. If 8 06 Nov 2014, 02:55
Display posts from previous: Sort by