Find all School-related info fast with the new School-Specific MBA Forum

It is currently 20 Oct 2014, 04:06

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

M15-03

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Manager
Manager
User avatar
Joined: 18 May 2012
Posts: 58
Concentration: Finance, Marketing
GMAT 1: 600 Q47 V25
GMAT 2: 670 Q49 V32
GMAT 3: 750 Q50 V41
Followers: 5

Kudos [?]: 58 [0], given: 18

M15-03 [#permalink] New post 01 Jun 2013, 21:31
1
This post was
BOOKMARKED
The sequence A1 , A2 , ... is defined such that An+1 = \frac{An}{n+1} for all n>1 . How many terms of the sequence is greater than \frac{1}{2} ?

(1) A2 =5

(2) A1 −A2 =5

-Doubt --
1. We are specifically told tha the function is only valid for n>1, however the solution assumes that A2 = \frac{A1}{2} then shouldnt we say for all n>=1 ?

Also shouldnt the question say-- how many terms are (not is)
_________________

Focusing on apps..
|GMAT Debrief|TOEFL Debrief|

Manager
Manager
avatar
Joined: 27 Feb 2012
Posts: 138
Followers: 1

Kudos [?]: 20 [0], given: 22

Re: M15-03 [#permalink] New post 01 Jun 2013, 23:41
rohanGmat wrote:
The sequence A1 , A2 , ... is defined such that An+1 = \frac{An}{n+1} for all n>1 . How many terms of the sequence is greater than \frac{1}{2} ?

(1) A2 =5

(2) A1 −A2 =5

-Doubt --
1. We are specifically told tha the function is only valid for n>1, however the solution assumes that A2 = \frac{A1}{2} then shouldnt we say for all n>=1 ?

Also shouldnt the question say-- how many terms are (not is)


I agree with you on this. There should be something said on no. of terms.
_________________

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Please +1 KUDO if my post helps. Thank you.

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23331
Followers: 3599

Kudos [?]: 28591 [0], given: 2803

Re: M15-03 [#permalink] New post 02 Jun 2013, 03:19
Expert's post
rohanGmat wrote:
The sequence A1 , A2 , ... is defined such that An+1 = \frac{An}{n+1} for all n>1 . How many terms of the sequence is greater than \frac{1}{2} ?

(1) A2 =5

(2) A1 −A2 =5

-Doubt --
1. We are specifically told tha the function is only valid for n>1, however the solution assumes that A2 = \frac{A1}{2} then shouldnt we say for all n>=1 ?

Also shouldnt the question say-- how many terms are (not is)


The sequence defined by some formula for all n>1, so it's valid for A2 (n=2>1).

The sequence A_1, A_2, ... is defined such that A_{n+1}=\frac{A_{n}}{n+1} for all n>1. How many terms of the sequence are greater than 1/2?

Basically we have a sequence of numbers which is defined with some formula. For example: A_{2}=\frac{A_{1}}{1+1}, A_{3}=\frac{A_{2}}{2+1}, A_{4}=\frac{A_{3}}{3+1}, ... The question asks: how many numbers from the sequence are greater than 1/2. Notice that if we knew ANY term of the sequence we would be able to get all the other terms/numbers and thus answer the question.

(1) A_2=5. As discussed above this statement is sufficient as we can write down all the terms. For example: A_{2}=\frac{A_{1}}{1+1}=5 --> A_1=10. A_{3}=\frac{A_{2}}{2+1}=\frac{5}{3}, and so on.

(2) A_1-A_2=5 --> A_1-\frac{A_{1}}{1+1}=5 --> we can solve for A_1 and thus will have the same case of knowing one term. Sufficient.

Answer: D.

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Manager
Manager
User avatar
Joined: 18 May 2012
Posts: 58
Concentration: Finance, Marketing
GMAT 1: 600 Q47 V25
GMAT 2: 670 Q49 V32
GMAT 3: 750 Q50 V41
Followers: 5

Kudos [?]: 58 [0], given: 18

Re: M15-03 [#permalink] New post 02 Jun 2013, 09:32
Bunuel wrote:
rohanGmat wrote:
The sequence A1 , A2 , ... is defined such that An+1 = \frac{An}{n+1} for all n>1 . How many terms of the sequence is greater than \frac{1}{2} ?

(1) A2 =5

(2) A1 −A2 =5

-Doubt --
1. We are specifically told tha the function is only valid for n>1, however the solution assumes that A2 = \frac{A1}{2} then shouldnt we say for all n>=1 ?

Also shouldnt the question say-- how many terms are (not is)


The sequence defined by some formula for all n>1, so it's valid for A2 (n=2>1).

The sequence A_1, A_2, ... is defined such that A_{n+1}=\frac{A_{n}}{n+1} for all n>1. How many terms of the sequence are greater than 1/2?

Basically we have a sequence of numbers which is defined with some formula. For example: A_{2}=\frac{A_{1}}{1+1}, A_{3}=\frac{A_{2}}{2+1}, A_{4}=\frac{A_{3}}{3+1}, ... The question asks: how many numbers from the sequence are greater than 1/2. Notice that if we knew ANY term of the sequence we would be able to get all the other terms/numbers and thus answer the question.

(1) A_2=5. As discussed above this statement is sufficient as we can write down all the terms. For example: A_{2}=\frac{A_{1}}{1+1}=5 --> A_1=10. A_{3}=\frac{A_{2}}{2+1}=\frac{5}{3}, and so on.

(2) A_1-A_2=5 --> A_1-\frac{A_{1}}{1+1}=5 --> we can solve for A_1 and thus will have the same case of knowing one term. Sufficient.

Answer: D.

Hope it helps.

Hi Bunuel,
I am still not convinced. -- "The sequence defined by some formula for all n>1, so it's valid for A2 (n=2>1)" -- because in the function given you put n=1 to get A2 = A1/2 - yet in the next line we are told the function is only valid for all n>1.
Shouldnt it say n>=1
_________________

Focusing on apps..
|GMAT Debrief|TOEFL Debrief|

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23331
Followers: 3599

Kudos [?]: 28591 [0], given: 2803

Re: M15-03 [#permalink] New post 04 Jun 2013, 06:26
Expert's post
rohanGmat wrote:
Bunuel wrote:
rohanGmat wrote:
The sequence A1 , A2 , ... is defined such that An+1 = \frac{An}{n+1} for all n>1 . How many terms of the sequence is greater than \frac{1}{2} ?

(1) A2 =5

(2) A1 −A2 =5

-Doubt --
1. We are specifically told tha the function is only valid for n>1, however the solution assumes that A2 = \frac{A1}{2} then shouldnt we say for all n>=1 ?

Also shouldnt the question say-- how many terms are (not is)


The sequence defined by some formula for all n>1, so it's valid for A2 (n=2>1).

The sequence A_1, A_2, ... is defined such that A_{n+1}=\frac{A_{n}}{n+1} for all n>1. How many terms of the sequence are greater than 1/2?

Basically we have a sequence of numbers which is defined with some formula. For example: A_{2}=\frac{A_{1}}{1+1}, A_{3}=\frac{A_{2}}{2+1}, A_{4}=\frac{A_{3}}{3+1}, ... The question asks: how many numbers from the sequence are greater than 1/2. Notice that if we knew ANY term of the sequence we would be able to get all the other terms/numbers and thus answer the question.

(1) A_2=5. As discussed above this statement is sufficient as we can write down all the terms. For example: A_{2}=\frac{A_{1}}{1+1}=5 --> A_1=10. A_{3}=\frac{A_{2}}{2+1}=\frac{5}{3}, and so on.

(2) A_1-A_2=5 --> A_1-\frac{A_{1}}{1+1}=5 --> we can solve for A_1 and thus will have the same case of knowing one term. Sufficient.

Answer: D.

Hope it helps.

Hi Bunuel,
I am still not convinced. -- "The sequence defined by some formula for all n>1, so it's valid for A2 (n=2>1)" -- because in the function given you put n=1 to get A2 = A1/2 - yet in the next line we are told the function is only valid for all n>1.
Shouldnt it say n>=1


Edited the question:
Attachment:
M15-03.png
M15-03.png [ 5.46 KiB | Viewed 386 times ]
Is it clearer now?
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: M15-03   [#permalink] 04 Jun 2013, 06:26
Display posts from previous: Sort by

M15-03

  Question banks Downloads My Bookmarks Reviews Important topics  

Moderators: Bunuel, WoundedTiger



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

Powered by phpBB © phpBB Group and phpBB SEO

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®.