Is p = |p|? (1) p is prime (2) p is even

Question

Is p = |p|?

(1) p is prime 
(2) p is even

M36-115

Bunuel · Accepted Answer

Official Solution:

Is  p = |p| ? 
 
Notice that the question basically asks whether  p  is positive or 0.
 
(1)  p  is prime
 
Only positive numbers can be primes, so  p  is positive and thus  p = |p| . Sufficient.
 
(2)  p  is even
 
 p  can be positive, say 10, as well as negative, say -10. Not sufficient.

Answer: A

Chethan92 · Answer

Question: Whether P = +P or -P.

From statement 1:

P is prime. Only positive integers are prime, then P = P.
Sufficient.

From statement 2:

P is even, Only positive integers are even, then P = P.
Sufficient.

D is the answer.

GMATBusters · Answer

If p is positive, mod p = p
If p is negative, mod p = -p

1) Prime numbers are defined for positive integers, so statement 1 us sufficient.

2) odd and even numbers are defined only in reference to the set of integers (..., −3, −2, −1, 0, 1, 2, 3, ...), all negative numbers can also be either odd or even.
So  statement 2 is not sufficient .

Answer = A

shashankism · Answer

Question: Is p = |p|

Statement 1 : P is a prime.. All prime numbers are positive numbers..
Sufficient.

Statement 2 : P is even. But even numbers can be both positive or negative. 
Not Sufficient.

Answer A

Chethan92 · Answer

Had no info about the highlighted portion. Thanks, sir.

shashankism · Answer

Yes we don't take care of these things and ultimately do mistake.. Good that this question came up so that we added new info in our preparation matrix.

Archit3110 · Answer

From 1: p is prime : p can be 2,3,5,7... 
not sufficient

From 2: p is even : 2,4,6,8... 
not sufficient

From 1 & 2: only possible value is 2
IMO C.

Archit3110 · Answer

gmatbusters 
as per statement 1 , wont we get many values of P i.e 2,3,5,7 , i think it would be insufficient

Chethan92 · Answer

Hey Archit,

The question is just asking whether P = P. It'll always be true. Hence A is sufficient.

Posted from my mobile device

shashankism · Answer

The question is only asking if p is positive or not. So only Value you get is "Yes it is +ve".

Archit3110 · Answer

Afc0892  
thats what i thought so, but ideally in DS questions we can say the statement to be sufficient if we have a definite value..

A would be correct if we need to only prove that the relation P=IPI is true , where as C would give us a definite value and as P = +2 which I think would be correct option..

I some what do agree with option A as prime no are only +ve no. so p=lpl would always stand true for all prime no. isnt it in DS that we need to find a definite answer /value to make the statement stand sufficient?

GMATinsight  : 
Sir could you please see into this question ...

GMATBusters · Answer

Hi  Archit3110

You are right that in DS , we need a definite answer.

But the answer should be definite for the question asked in the question stem.

Question: is Mod p = p

if Answer = yes , it is definite

if answer = No, it is definite

but if Answer = Yes in some cases and No in some cases, it is not definite.

As per Statement1: As all prime numbers are positive, hence Mod p = p, Answer = yes , it is definite.

As per Statement 2:

if p = 2, answer = yes

if p = -2, answer = No, Answer = Yes in some cases and No in some cases. Hence it is NOT DEFINITE.

Answer = A

Bunuel · Answer

There are two types of data sufficiency questions:

1. YES/NO DS Questions:

In a Yes/No Data Sufficiency questions, statement(s) is sufficient if the answer is “always yes” or “always no” while a statement(s) is insufficient if the answer is "sometimes yes" and "sometimes no".

2. VALUE DS QUESTIONS:

When a DS question asks about the value of some variable, then the statement(s) is sufficient ONLY if you can get the single numerical value of this variable.

Strategies and Tactics for DS Section

GMAT Tip of the Week: The Data Sufficiency Reward System 
 GMAT Tip of the Week: The Heart of Data Sufficiency 
 GMAT Tip of The Week: Tonya Harding Teaches Data Sufficiency 
 C-Trap Questions 
Veritas Prep blog on  C-Trap .
Manhattan GMAT blog on  C-Trap .
 Another Manhattan GMAT blog  on C-Trap.
 Warning: Don't Fall Into the C Trap on Data Sufficiency Questions 
 Easy (A)/(B) Trap in Data Sufficiency Questions on the GMAT 
 How to Breakdown Data Sufficiency Sequence Questions on the GMAT 
 How to Make Abstract Data Sufficiency Questions More Concrete 
 Math Knowledge is Often Insufficient on Data Sufficiency 
 Why You Should Do the Math on Data Sufficiency GMAT Questions 
 GMAT Tip of the Week: No Resolution! 
 GMAT Tip of the Week: LeBron James Says Don't Be Cavalier About Your Initial Data Sufficiency Decision 
 Data Sufficiency: Why Are you Here? 
 GMAT Tip of the Week: Kanye West Teaches You How To Live The Data Sufficiency Good Life 
 When Do You Have Enough Information on Data Sufficiency GMAT Questions?

For more check  Ultimate GMAT Quantitative Megathread

Hope it helps.

shashankism · Answer

Hi Archit3110 , That's the beauty of GMAT DS questions.. You have to be very sure what question is asking. Lets take an example.. If I ask you .. Do you want to visit a Hill station ? The answer you will give is either Yes or No or Maybe. So, Yes or No are definite answer and Maybe is not definite. Here there can be many hillstation but that doesn't matter as question is asked if you want to visit or not. Yes - Definite No - Definite Maybe - Indefinite. If you started thinking kulu, manali, Shimla .. you are gone

. So, Try to analyse question first what the question is asking. The actual GMAT questions will be so simple that you can sometimes fall in the trick and mark wrong answers. Hope that helps.

GMATinsight · Answer

Archit3110

We combine two statements only when the statements alone are NOT sufficient to answer the question

Here the question is "Is p = |p|?" which needs to be answered in the form of YES/NO

As soon as we use the first statement which states that p is Prime (which are essentially positive integers) then we can answer the question with a  Definitely YES  hence statement 1 alone is sufficient.

Since this alone is sufficient so we can strike off option C at this stage only so that the question of C to be a potential answer does NOT arise while using statement 2 alone.

I hope this helps!!1

Archit3110 · Answer

Here the question is "Is p = |p|?" which needs to be answered in the form of YES/NO

As soon as we use the first statement which states that p is Prime (which are essentially positive integers) then we can answer the question with a Definitely YES hence statement 1 alone is sufficient.

Since this alone is sufficient so we can strike off option C at this stage only so that the question of C to be a potential answer does NOT arise while using statement 2 alone.

I hope this helps!!1[/quote]

GMATinsight :

For elimination of options I do follow AD/BCE rule in DS..

Sir, I understood where I was going wrong in my assumption ..

.. thanks for replying..

Bunuel · Answer

Par of  GMAT CLUB'S New Year's Quantitative Challenge Set

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Is p = |p|? (1) p is prime (2) p is even

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GMAT Data Sufficiency (DS) Questions

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