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

It is currently 15 Oct 2019, 19:13

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 x is a positive integer and 4^x – 3 = y, which of the following CAN

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58340
If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 22 Jun 2018, 00:14
1
11
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

94% (00:55) correct 6% (01:02) wrong based on 912 sessions

HideShow timer Statistics

Most Helpful Expert Reply
e-GMAT Representative
User avatar
V
Joined: 04 Jan 2015
Posts: 3074
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 22 Jun 2018, 03:31
8
3

Solution



Given:
    • x is a positive integer
    • \(4^x – 3 = y\)

To find:
    • From the given options, which one cannot be the value of y

Approach and Working:

Apart from checking with the options, there is one more way of figuring out the correct answer
From the given expression \(4^x – 3 = y\),
    • \(4^x = y + 3\)

Now, for any value of x, \(4^x\) will always end with either 4 of 6
    • Hence, y must be ending with either 1 or 3

From the given options, only option B is not ending with either 1 or 3

Hence, the correct answer is option B.

Answer: B
_________________
General Discussion
Intern
Intern
avatar
B
Joined: 08 Jul 2017
Posts: 15
Location: Greece
GPA: 3.31
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 22 Jun 2018, 00:26
If x=1: 4^1 - 3 = 1
If x=2: 4^2 - 3 = 13
If x=3: 4^3 - 3 = 61
If x=4: 4^4 - 3 = 253

The only value that y cannot take is 7.

The correct answer is B.
Senior Manager
Senior Manager
User avatar
G
Joined: 13 Feb 2018
Posts: 451
GMAT 1: 640 Q48 V28
Premium Member
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 22 Jun 2018, 01:29
OG 2019? very interesting
Has "bb" already made an excel spreadsheet about it?
If yes, please give me the link
Intern
Intern
avatar
B
Joined: 03 Aug 2014
Posts: 19
Schools: Kellogg '21 (A)
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 22 Jun 2018, 02:15
1
1
4x-3 = y => 4x = y+3

This implies that y+3 should be a multiple of 4. Quickly scanning the options reveal that for option B, 7+3 = 10 is not a multiple of 4.

Sent from my Pixel using GMAT Club Forum mobile app
VP
VP
User avatar
D
Joined: 31 Oct 2013
Posts: 1471
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
CAT Tests
If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 22 Jun 2018, 02:16
Bunuel wrote:
If x is a positive integer and \(4^x – 3 = y\), which of the following CANNOT be a value of y ?


A. 1

B. 7

C. 13

D. 61

E. 253



NEW question from GMAT® Official Guide 2019


(PS04797)



Note:

x = positive integer

Given,

\(4^x\)-3=y

we are asked to find out which can't be the value of y. No specific value of x is given.

Trail and error is the way to get the correct answer. Assume the value of x = 1 , 2 , 3 , 4. All the option matches except B.

\(4^1\)-3=1
\(4^2\)-3=13
\(4^3\)-3=61
\(4^4\)-3=253

Thus , B is the correct answer.
Board of Directors
User avatar
D
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4778
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 20 Aug 2019, 07:52
Bunuel wrote:
If x is a positive integer and \(4^x – 3 = y\), which of the following CANNOT be a value of y ?


A. 1

B. 7

C. 13

D. 61

E. 253



NEW question from GMAT® Official Guide 2019


(PS04797)


(A) \(4^1 - 3 = 1\) ; Possible
(C) \(4^2 - 3 = 13\) ; Possible
(D) \(4^3 - 3 = 61\) ; Possible
(E) \(4^4 - 3 = 253\) ; Possible

Thus, Answer must be (B) 7
_________________
Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )
SVP
SVP
User avatar
P
Joined: 03 Jun 2019
Posts: 1689
Location: India
Premium Member Reviews Badge CAT Tests
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

Show Tags

New post 15 Sep 2019, 03:08
Bunuel wrote:
If x is a positive integer and \(4^x – 3 = y\), which of the following CANNOT be a value of y ?


A. 1

B. 7

C. 13

D. 61

E. 253



NEW question from GMAT® Official Guide 2019


(PS04797)


Given: x is a positive integer and \(4^x – 3 = y\)

Asked: Which of the following CANNOT be a value of y ?

\(4^x – 3 = y\)

A. 1
4^x - 3 = 1
4^x = 4
x =1

B. 7
4^x - 3 = 7
4^x = 10
x is not an integer

C. 13
4^x - 3 = 13
4^x = 16
x = 2

D. 61
4^x = 61+3 = 64
x = 3

E. 253
4^x = 253+3 = 256
x = 4

IMO B
_________________
"Success is not final; failure is not fatal: It is the courage to continue that counts."

Please provide kudos if you like my post. Kudos encourage active discussions.

My GMAT Resources: -

Efficient Learning
All you need to know about GMAT quant

Tele: +91-11-40396815
Mobile : +91-9910661622
E-mail : kinshook.chaturvedi@gmail.com
GMAT Club Bot
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN   [#permalink] 15 Sep 2019, 03:08
Display posts from previous: Sort by

If x is a positive integer and 4^x – 3 = y, which of the following CAN

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





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