It is currently 20 Mar 2019, 19:17

### 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

# The sequence S is defined by Sn = 2(Sn – 1) – 4 for each int

Author Message
TAGS:
GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1776 [0], given: 397

The sequence S is defined by Sn = 2(Sn – 1) – 4 for each int [#permalink]  25 Jul 2018, 17:22
Expert's post
00:00

Question Stats:

83% (00:38) correct 16% (03:26) wrong based on 6 sessions
The sequence S is defined by $$S_n = 2(S_{n – 1}) – 4$$ for each integer n ≥ 2. If $$S_1 = 6$$, what is the value of $$S_5$$?

(A) –20
(B) 16
(C) 20
(D) 24
(E) 36
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1776 [0], given: 397

Re: The sequence S is defined by Sn = 2(Sn – 1) – 4 for each int [#permalink]  11 Aug 2018, 16:51
Expert's post
Explanation

The sequence $$S_n = 2(S_{n - 1}) - 4$$ can be read as “to get any term in sequence S, double the previous term and subtract 4.”

The problem gives $$S_1$$ (the first term) and asks for $$S_5$$ (the fifth term):

 6 $$S_1$$ $$S_2$$ $$S_3$$ $$S_4$$ $$S_5$$

To get any term, double the previous term and subtract 4. To get $$S_2$$, double $$S_1$$ (which is 6) and subtract 4: $$S_2 = 2(6) - 4 = 8$$.

Continue doubling each term and subtracting 4 to get the subsequent term:

 6 8 12 20 36 $$S_1$$ $$S_2$$ $$S_3$$ $$S_4$$ $$S_5$$

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Re: The sequence S is defined by Sn = 2(Sn – 1) – 4 for each int   [#permalink] 11 Aug 2018, 16:51
Display posts from previous: Sort by