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

It is currently 15 Jul 2018, 14:30

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

If f(n) = xa^n, what is the value of f(5) ?

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

Hide Tags

1 KUDOS received
SVP
SVP
User avatar
V
Status: Preparing for the GMAT
Joined: 02 Nov 2016
Posts: 1593
Location: Pakistan
GPA: 3.39
Premium Member CAT Tests
If f(n) = xa^n, what is the value of f(5) ? [#permalink]

Show Tags

New post 02 Apr 2017, 12:07
1
4
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

33% (01:22) correct 67% (01:05) wrong based on 103 sessions

HideShow timer Statistics

If f(n) = xa^n, what is the value of f(5) ?

(1) f(0) = 3
(2) f(4) = 48

_________________

Official PS Practice Questions
Press +1 Kudos if this post is helpful

Expert Post
Top Contributor
1 KUDOS received
CEO
CEO
User avatar
P
Joined: 12 Sep 2015
Posts: 2630
Location: Canada
If f(n) = xa^n, what is the value of f(5) ? [#permalink]

Show Tags

New post 02 Apr 2017, 13:06
1
Top Contributor
2
SajjadAhmad wrote:
If f(n) = xa^n, what is the value of f(5) ?

(1) f(0) = 3
(2) f(4) = 48


Target question: What is the value of f(5)?

Given: f(n) = xa^n

Statement 1: f(0) = 3
In other words, x(a^0) = 3
Since a^0 = 1, we can write: (x)(1) = 3
This tells us that x = 3
So, our function now looks like this: f(n) = 3a^n
Since we still don't know the value of a, this is NOT enough information to determine the value of f(5)
Since we cannot answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: f(4) = 48
In other words, x(a^4) = 48
There are several values of x and a that satisfy statement 2. Here are two:
Case a: x = 3 and a = 2. Notice that x(a^4) = 48 turns into 3(2^4) = 48, which works. In this case f(5) = 3(2^5) = 96
Case b: x = 3 and a = -2. Notice that x(a^4) = 48 turns into 3[(-2)^4] = 48, which works. In this case f(5) = 3[(-2)^5] = -96
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that x = 3
Statement 2 tells us that, when x = 3, either a = 2 or a = -2
In other words, we still have 2 possible cases that satisfy BOTH statements:
Case a: x = 3 and a = 2. Notice that x(a^4) = 48 turns into 3(2^4) = 48, which works. In this case f(5) = 3(2^5) = 96
Case b: x = 3 and a = -2. Notice that x(a^4) = 48 turns into 3[(-2)^4] = 48, which works. In this case f(5) = 3[(-2)^5] = -96
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

RELATED VIDEO

_________________

Brent Hanneson – Founder of gmatprepnow.com

Image

If f(n) = xa^n, what is the value of f(5) ?   [#permalink] 02 Apr 2017, 13:06
Display posts from previous: Sort by

If f(n) = xa^n, what is the value of f(5) ?

  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®.