GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 18 Jan 2020, 04:04 ### 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.  # If x is a positive integer and 4^x – 3 = y, which of the following CAN

Author Message
TAGS:

### Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 60460
If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

### Show Tags

1
13 00:00

Difficulty:

(N/A)

Question Stats: 94% (00:56) correct 6% (01:05) wrong based on 1030 sessions

### HideShow timer Statistics

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)

_________________
e-GMAT Representative V
Joined: 04 Jan 2015
Posts: 3209
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

### Show Tags

10
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.

_________________
##### General Discussion
Intern  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

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.

Senior Manager  P
Joined: 13 Feb 2018
Posts: 496
GMAT 1: 640 Q48 V28
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

### Show Tags

OG 2019? very interesting
Intern  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

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  D
Joined: 31 Oct 2013
Posts: 1494
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

### Show Tags

1
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 D
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4856
Location: India
GPA: 3.5
Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

### Show Tags

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  D
Joined: 03 Jun 2019
Posts: 1936
Location: India
GMAT 1: 690 Q50 V34 Re: If x is a positive integer and 4^x – 3 = y, which of the following CAN  [#permalink]

### Show Tags

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 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  