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

 It is currently 20 Oct 2019, 20:53 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.  Is the sum of the integers x and y a prime number?

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

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58435
Is the sum of the integers x and y a prime number?  [#permalink]

Show Tags 00:00

Difficulty:   25% (medium)

Question Stats: 82% (01:10) correct 18% (00:58) wrong based on 22 sessions

HideShow timer Statistics

Is the sum of the integers x and y a prime number?

(1) x is an even prime number.
(2) y is a prime number between 10 and 20.

_________________
Manager  G
Joined: 10 Apr 2018
Posts: 244
Location: India
Concentration: Entrepreneurship, Strategy
GMAT 1: 680 Q48 V34 GPA: 3.3
Is the sum of the integers x and y a prime number?  [#permalink]

Show Tags

We are required to check whether x+y is a prime number.

(1) 2 is the only even prime number, so x=2
However, we don't know the value of y.
Thus, insufficient.

(2) As per this statement, y=13,17, or 19.
Also, we don't know the value of x.
Thus, insufficient.

From (1) and (2) together, x+y=15,19,or 21.
Thus, insufficient.

Therefore, answer is option E.
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8023
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Is the sum of the integers x and y a prime number?  [#permalink]

Show Tags

Bunuel wrote:
Is the sum of the integers x and y a prime number?

(1) x is an even prime number.
(2) y is a prime number between 10 and 20.

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.
Visit https://www.mathrevolution.com/gmat/lesson for details.

Since we have 2 variables (x and y) and 0 equations, C is most likely the answer. So, we should consider conditions 1) & 2) together first. After comparing the number of variables and the number of equations, we can save time by considering conditions 1) & 2) together first.

Conditions 1) & 2)
If x = 2 and y = 11, then x + y = 13 is a prime number and the answer is 'yes'.
If x = 2 and y = 13, then x + y = 15 is not a prime number and the answer is 'no'.

Since both conditions together do not yield a unique solution, they are not sufficient.

Therefore, E is the answer.

Normally, in problems which require 2 equations, such as those in which the original conditions include 2 variables, or 3 variables and 1 equation, or 4 variables and 2 equations, each of conditions 1) and 2) provide an additional equation. In these problems, the two key possibilities are that C is the answer (with probability 70%), and E is the answer (with probability 25%). Thus, there is only a 5% chance that A, B, or D is the answer. This occurs in common mistake types 3 and 4. Since C (both conditions together are sufficient) is the most likely answer, we save time by first checking whether conditions 1) and 2) are sufficient, when taken together. Obviously, there may be cases in which the answer is A, B, D, or E, but if conditions 1) and 2) are NOT sufficient when taken together, the answer must be E.
_________________
Senior Manager  P
Joined: 30 Sep 2017
Posts: 380
Concentration: Technology, Entrepreneurship
GMAT 1: 720 Q49 V40 GPA: 3.8
WE: Engineering (Real Estate)
Is the sum of the integers x and y a prime number?  [#permalink]

Show Tags

Q. Is (x+y) prime?

(1) x is an even prime number, so x=2.
We don't know y value.
NOT SUFFICIENT.

(2) y is a prime number between 10 and 20, so y can be 11,13,17, or 19.
We don't know x value.
NOT SUFFICIENT.

(1)+(2),
(x+y) can be 13,15,19,or 21. (x+y) may or may not be a prime number.
NOT SUFFICIENT

Final answer is E
Senior Manager  G
Joined: 07 Mar 2019
Posts: 329
Location: India
GMAT 1: 580 Q43 V27 WE: Sales (Energy and Utilities)
Re: Is the sum of the integers x and y a prime number?  [#permalink]

Show Tags

Is the sum of the integers x and y a prime number?
x + y = prime ??

(1) x is an even prime number.
x = 2
As y is unknown so it can take any value. Thus

INSUFFICIENT.

(2) y is a prime number between 10 and 20.

Possible values of y are 11, 13 17 and 19.
Since x is unknown and it can take any value, statement is not sufficient.

INSUFFICIENT.

Together 1 and 2
Possible values of 'x + y' are 13, 1, 19 and 21. So two values are prime and two are not.Hence

INSUFFICIENT.

_________________
Ephemeral Epiphany..!

GMATPREP1 590(Q48,V23) March 6, 2019
GMATPREP2 610(Q44,V29) June 10, 2019
GMATPREPSoft1 680(Q48,V35) June 26, 2019 Re: Is the sum of the integers x and y a prime number?   [#permalink] 11 Oct 2019, 19:42
Display posts from previous: Sort by

Is the sum of the integers x and y a prime number?

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

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