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

 It is currently 19 Jun 2013, 19:58

The infinite sequence a1, a2,...,an is defined such that an

Author Message
TAGS:
Manager
Joined: 25 Feb 2008
Posts: 55
Followers: 0

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

The infinite sequence a1, a2,...,an is defined such that an [#permalink]  23 Jul 2008, 07:20
The infinite sequence a1, a2,...,an is defined such that an = (n+2) / n for all n ≥ 1. What is the product of the first 10 terms of the sequence?

(A) 45
(B) 66
(C) 90
(D) 121
(E) 132
Quick way to solve this.
GMAT Instructor
Joined: 24 Jun 2008
Posts: 973
Location: Toronto
Followers: 174

Kudos [?]: 454 [0], given: 3

Re: The Infinite sequence [#permalink]  24 Jul 2008, 06:19
Capthan wrote:
The infinite sequence a1, a2,...,an is defined such that an = (n+2) / n for all n ≥ 1. What is the product of the first 10 terms of the sequence?

(A) 45
(B) 66
(C) 90
(D) 121
(E) 132
Quick way to solve this.

The first ten terms are 3/1, 4/2, 5/3, ..., 11/9, 12/10

The product of these terms is (12*11*10*...*4*3)/10! = 12*11/2 = 66
_________________

Nov 2011: After years of development, I am now making my advanced Quant books and high-level problem sets available for sale. Contact me at ianstewartgmat at gmail.com for details.

Private GMAT Tutor based in Toronto

Senior Manager
Joined: 19 Mar 2008
Posts: 360
Followers: 1

Kudos [?]: 12 [0], given: 0

Re: The Infinite sequence [#permalink]  24 Jul 2008, 08:38
IanStewart wrote:
Capthan wrote:
The infinite sequence a1, a2,...,an is defined such that an = (n+2) / n for all n ≥ 1. What is the product of the first 10 terms of the sequence?

(A) 45
(B) 66
(C) 90
(D) 121
(E) 132
Quick way to solve this.

The first ten terms are 3/1, 4/2, 5/3, ..., 11/9, 12/10

The product of these terms is (12*11*10*...*4*3)/10! = 12*11/2 = 66

66

just list out the number. then you will get it in a pretty fast way
Director
Joined: 01 Jan 2008
Posts: 635
Followers: 3

Kudos [?]: 114 [0], given: 1

Re: The Infinite sequence [#permalink]  24 Jul 2008, 17:04
(11*12)/(1*2)=11*6 = 66 -> B
Re: The Infinite sequence   [#permalink] 24 Jul 2008, 17:04
Similar topics Replies Last post
Similar
Topics:
Infinite Sequence The infinite sequence a1, a2, , an, is 7 21 Jun 2006, 17:12
The infinite sequence a1, a2,..., an,... is such that a1 = 2 03 Jul 2007, 06:57
1 The infinite sequence a1, a2,...,an is defined such that an 5 23 Jul 2008, 07:21
3 The infinite sequence a1, a2, …, an, … is such that a1=2 9 30 Aug 2010, 10:26
1 The infinite sequence a1, a2,...,an is defined such that an 11 15 Nov 2010, 18:19
Display posts from previous: Sort by