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

It is currently 19 Sep 2018, 21:58

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.

Close

Request Expert Reply

Confirm Cancel

In the sequence T, the first term is the non-zero number a, and each..

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Senior Manager
Senior Manager
User avatar
P
Joined: 12 Feb 2015
Posts: 428
Premium Member CAT Tests
In the sequence T, the first term is the non-zero number a, and each..  [#permalink]

Show Tags

New post 02 Jul 2018, 09:20
1
00:00
A
B
C
D
E

Difficulty:

  85% (hard)

Question Stats:

31% (01:50) correct 69% (01:23) wrong based on 36 sessions

HideShow timer Statistics


In the sequence T, the first term is the non-zero number a, and each term after the first term is equal to the non-zero number r multiplied by the previous term. What is the value of the fourth term of the sequence?

1. The sum of the first 2 terms of the sequence is 16.
2. The 18th term of the sequence is 81 times the 14th term of the sequence.

_________________

"Please hit :thumbup: +1 Kudos if you like this post" :student_man:

_________________
Manish :geek:

"Only I can change my life. No one can do it for me"

Manager
Manager
avatar
G
Joined: 28 Jul 2016
Posts: 135
Premium Member
Re: In the sequence T, the first term is the non-zero number a, and each..  [#permalink]

Show Tags

New post 02 Jul 2018, 10:26
1
1st term: \(T_1\)= \(a\)
2nd term \(T_2\) =\(a*r\)
3rd term \(T_3\)= \(a*r*r = a*r^2\)
n-th term \(T_n\) = \(a*r^{n-1}\)

1) \(a + a*r = 16\)
\(a*(1+r) = 16\)
We can have muptiple pairs of a and r that satisfy this equation
So Not sufficient

2) So \(18_{th}\) term: \(T_{18}\)= \(a*r^{17}\)
\(14_{th}\) term: \(T_{14}= a*r^{13}\)
\(\frac{T_{18}}{T_{14}} = \frac{a*r^{17}}{a*r^{13}} = r^{4} = 81\)
\(r = \pm 3\)
So Not sufficient

Both 1) and 2) don't give us uniqe combination of a and r to define \(T_4\)
If r = +3, then a = +4, \(T_4 = 64\)
If r = -3, then a = -8, \(T_4 = -0.001953125\)
So Not sufficient

Answer E
Manager
Manager
avatar
G
Joined: 28 Jul 2016
Posts: 135
Premium Member
Re: In the sequence T, the first term is the non-zero number a, and each..  [#permalink]

Show Tags

New post 02 Jul 2018, 10:27
This is geometrical progression
and we use formula to find n-th element of geometrical progression
Re: In the sequence T, the first term is the non-zero number a, and each.. &nbs [#permalink] 02 Jul 2018, 10:27
Display posts from previous: Sort by

In the sequence T, the first term is the non-zero number a, and each..

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Events & Promotions

PREV
NEXT


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

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.