The sequence is defined as follows: A(n) = n/(n+1). : PS Archive
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 24 Jan 2017, 13:36

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

The sequence is defined as follows: A(n) = n/(n+1).

Author Message
Manager
Joined: 06 Jul 2007
Posts: 161
Schools: CBS, MIT, Kellogg, Wharton
Followers: 3

Kudos [?]: 6 [0], given: 5

The sequence is defined as follows: A(n) = n/(n+1).  [#permalink]

Show Tags

01 Aug 2007, 07:25
00:00

Difficulty:

(N/A)

Question Stats:

100% (02:29) correct 0% (00:00) wrong based on 0 sessions

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The sequence is defined as follows:

A(n) = n/(n+1).

How many of the first 100 terms of this sequence are less than 0.891

A) 7
B) 8
C) 9
D)10
E) 12
Senior Manager
Joined: 04 Jun 2007
Posts: 346
Followers: 1

Kudos [?]: 29 [0], given: 0

Show Tags

01 Aug 2007, 07:58
raptr wrote:
The sequence is defined as follows:

A(n) = n/(n+1).

How many of the first 100 terms of this sequence are less than 0.891

A) 7
B) 8
C) 9
D)10
E) 12

It is B.

A(9) = 0.9
A(8) = 0.89

Therefore, 8 terms are less than 0.891.
Director
Joined: 16 May 2007
Posts: 549
Followers: 2

Kudos [?]: 59 [0], given: 0

Show Tags

01 Aug 2007, 08:08
i used brute force method to arrive at the numbers

1/2 , 2/3, 3/4, 4/5, 5/6 , 6/7 , 7/8, 8/9

all these are less than 0.891 .. others that follow inthis series are greater than 0.891. Hence B i.e 8 is the answer
Manager
Joined: 06 Jul 2007
Posts: 161
Schools: CBS, MIT, Kellogg, Wharton
Followers: 3

Kudos [?]: 6 [0], given: 5

Show Tags

01 Aug 2007, 09:38
OA is B) 8.

What I don't understand is how do you decide which term exactly is "the first term" and why [b]n[/b] can't be 0 or negative.

If n=0 -> n/n+1 = 0/1 = 0 and 0<0.891
Senior Manager
Joined: 04 Jun 2007
Posts: 346
Followers: 1

Kudos [?]: 29 [0], given: 0

Show Tags

01 Aug 2007, 09:47
raptr wrote:
OA is B) 8.

What I don't understand is how do you decide which term exactly is "the first term" and why n can't be 0 or negative.

If n=0 -> n/n+1 = 0/1 = 0 and 0<0.891

That question did pop in my mind.
For n=-1, A(n) is undefined. For all other negative values of n, A(n) will be greater than 1. So, even considering negative integers won't make much of a difference.

But as you rightly pointed out, n=0 does make a difference. Further the question does not even mention that n is an integer !!

All in all, I believe that it is not a very well constructed question (if, of course, you have copied down the question completely ). Any other opinions ??
Current Student
Joined: 28 Dec 2004
Posts: 3384
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 15

Kudos [?]: 283 [0], given: 2

Show Tags

01 Aug 2007, 10:31
No, it cant be B...cause we are not told if N is positive and greater than 0 or not..cause 0/1=0 which is less than 0.89 and thus the number should be 9...

I would say not knowing if N is positive and greater than 0...the number is 9 not 8...

any takers??
Intern
Joined: 08 Sep 2006
Posts: 34
Followers: 0

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

Show Tags

01 Aug 2007, 11:07
raptr wrote:
The sequence is defined as follows:

A(n) = n/(n+1).

How many of the first 100 terms of this sequence are less than 0.891

A) 7
B) 8
C) 9
D)10
E) 12

I initially looked at B) 8, but after looking for the typical GMAT traps, I tried A(0) ~ I think it should be C) 9 as well. In the GMAT, x/0 is undefined, but 0/x is not. right?
Manager
Joined: 06 Jul 2007
Posts: 161
Schools: CBS, MIT, Kellogg, Wharton
Followers: 3

Kudos [?]: 6 [0], given: 5

Show Tags

01 Aug 2007, 12:09
0/x i definitely not undefined. I picked "C" and it turned out to be the wrong answer. I tought I am missing something fundamental... obviously I am not. Or am I?

I copied the problem word for word. This is the explanation:

"Let's write out first 10 terms of this series: 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10, 10/11. Any subsequent element in this series is bigger than its predecessor. To answer the question we have to find the first element that is bigger than 0.891. It is the 9th element = 9/10 = 0.900; 8/9 = 0.888... is less than 0.891. Thus, there are only 8 elements in the whole series that are less than 0.891. "

As you can see, it doesn't consider n<1.

I have no explanation. The official answer is B) This is question #3 from Challenge #14.

->>> I am not aware of a rule against posting Challenge materials here, but if there is such a rule and I am violating it, I appologize.
Senior Manager
Joined: 14 Jun 2007
Posts: 399
Followers: 1

Kudos [?]: 14 [0], given: 0

Show Tags

01 Aug 2007, 12:19
raptr wrote:
0/x i definitely not undefined. I picked "C" and it turned out to be the wrong answer. I tought I am missing something fundamental... obviously I am not. Or am I?

I copied the problem word for word. This is the explanation:

"Let's write out first 10 terms of this series: 1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10, 10/11. Any subsequent element in this series is bigger than its predecessor. To answer the question we have to find the first element that is bigger than 0.891. It is the 9th element = 9/10 = 0.900; 8/9 = 0.888... is less than 0.891. Thus, there are only 8 elements in the whole series that are less than 0.891. "

As you can see, it doesn't consider n<1>>> I am not aware of a rule against posting Challenge materials here, but if there is such a rule and I am violating it, I appologize.

there is a rule, but don't worry... I had many problems with the challenges
as some of the answers/explanations are 'iffy'. I chose B - but everyone's objections are valid. I checked the GMAT OG math rules... it says the domain of a function can consist of only positive values and possible zero (not sure why we can't have negative values for a domain?)

so in this problem, i think unless the domain is restricted to positive values that answer is technically 9
01 Aug 2007, 12:19
Display posts from previous: Sort by