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

 It is currently 16 Oct 2019, 08:46 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  In a certain sequence a1, a2, ...an..., for n>1, each term is the sum

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

Hide Tags

Manager  G
Joined: 30 May 2018
Posts: 89
GMAT 1: 620 Q42 V34 WE: Corporate Finance (Commercial Banking)
In a certain sequence a1, a2, ...an..., for n>1, each term is the sum  [#permalink]

Show Tags

8 00:00

Difficulty:   65% (hard)

Question Stats: 52% (01:59) correct 48% (01:56) wrong based on 61 sessions

HideShow timer Statistics

In a certain sequence a1, a2, ...an..., for n>1, each term is the sum of all previous terms. If an=S, in terms of S, a(n+3)=?

(A) 3S
(B) 4S
(C) 6S
(D) 8S
(E) 9S
Manager  G
Joined: 21 Feb 2019
Posts: 125
Location: Italy
Re: In a certain sequence a1, a2, ...an..., for n>1, each term is the sum  [#permalink]

Show Tags

2
$$a_n = S$$
$$a_{n+1} = S + S = 2S$$
$$a_{n+2} = 2S + 2S = 4S$$
$$a_{n+3} = 4S + 4S = 8S$$
_________________
If you like my post, Kudos are appreciated! Thank you.

MEMENTO AUDERE SEMPER
Intern  B
Joined: 18 Jan 2019
Posts: 28
Re: In a certain sequence a1, a2, ...an..., for n>1, each term is the sum  [#permalink]

Show Tags

lucajava wrote:
$$a_n = S$$
$$a_{n+1} = S + S = 2S$$
$$a_{n+2} = 2S + 2S = 4S$$
$$a_{n+3} = 4S + 4S = 8S$$

can you explain the logic behind this?
Manager  G
Joined: 21 Feb 2019
Posts: 125
Location: Italy
Re: In a certain sequence a1, a2, ...an..., for n>1, each term is the sum  [#permalink]

Show Tags

1
Ish1996 each term is the sum of all previous terms, so if $$a_n = S$$, $$a_{n+1}$$ is equal to all previous terms of $$a_n$$, which give S as result, in addition to $$a_n$$ itself, which is S.
Repeat this reasoning for the following ones and you will get the correct answer.

Posted from my mobile device
_________________
If you like my post, Kudos are appreciated! Thank you.

MEMENTO AUDERE SEMPER Re: In a certain sequence a1, a2, ...an..., for n>1, each term is the sum   [#permalink] 22 Apr 2019, 01:45
Display posts from previous: Sort by

In a certain sequence a1, a2, ...an..., for n>1, each term is the sum

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

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