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What is the value of the integer n? (1) n(n + 2) = 15 (2) (n

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What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink] New post 30 Dec 2010, 16:27
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B
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Question Stats:

63% (01:53) correct 37% (00:50) wrong based on 284 sessions
What is the value of the integer n?

(1) n(n + 2) = 15
(2) (n + 2)^n = 125

I am not sure if the given ans is right
[Reveal] Spoiler: OA

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Last edited by Bunuel on 10 Jul 2013, 00:54, edited 1 time in total.
Edited the OA.
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Re: What is the value of the integer n....Exponents [#permalink] New post 30 Dec 2010, 16:45
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ajit257 wrote:
What is the value of the integer n?

(1) n(n + 2) = 15
(2) (n + 2)^n = 125

I am not sure if the given ans is right


What is the value of the integer n?

(1) n(n + 2) = 15 --> n^2+2n-15=0 --> (n+5)(n-3)=0 --> n=-5 or n=3. Not sufficient.

(2) (n + 2)^n = 125 --> as n is an integer then (n + 2)^n=125^1=5^3 (125 can be written as integer^integer only in those two ways), only n=3 works: (2+3)^3=5^3=125. Sufficient.

Answer: B.
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Re: What is the value of the integer n....Exponents [#permalink] New post 30 Dec 2010, 16:53
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Bunuel,
Thanks for the confirmation. I got the same. The given ans is wrong ...should be B.
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Re: What is the value of the integer n....Exponents [#permalink] New post 31 Dec 2010, 17:04
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C it is

statment 2) is not sufficient coz N can be a decimal value

from statement 1) we know that N= -5 or 3
by sustituting these values in statement 2), we know that N=3
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Re: What is the value of the integer n....Exponents [#permalink] New post 01 Jan 2011, 00:28
girishkakkar wrote:
C it is

statment 2) is not sufficient coz N can be a decimal value

from statement 1) we know that N= -5 or 3
by sustituting these values in statement 2), we know that N=3


The question clearly states
"What is the value of the integer n?"

So the answer should be B.
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Re: What is the value of the integer n....Exponents [#permalink] New post 01 Jan 2011, 07:12
but talking about statement 2), cant value of N be 3 or ANY decimal number? Since it is NOT stated in the question that "N is an integer". Correct me if I am wrong.
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Re: What is the value of the integer n....Exponents [#permalink] New post 01 Jan 2011, 07:18
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girishkakkar wrote:
but talking about statement 2), cant value of N be 3 or ANY decimal number? Since it is NOT stated in the question that "N is an integer". Correct me if I am wrong.


Question is: What is the value of the integer n? So the stem explicitly says that n is an integer.
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Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink] New post 04 Jan 2012, 09:18
A GOOD TRICKY QUESTION.
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Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink] New post 04 Jan 2012, 13:14
Agree with Buneul. If n is integer, them then S2 has to be an integer.

1. Clearly insufficient, two roots = -5,3
2. Since n is integer, only n that satisfies this equation is n = 3. Sufficient

+B.
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Re: What is the value of the integer n....Exponents [#permalink] New post 02 Jan 2013, 07:53
Bunuel wrote:
ajit257 wrote:
What is the value of the integer n?

(1) n(n + 2) = 15
(2) (n + 2)^n = 125



What is the value of the integer n?

(1) n(n + 2) = 15 --> n^2+2n-15=0 --> (n+5)(n-3)=0 --> n=-5 or n=3. Not sufficient.

Answer: B.


Dear Bunuel,

My fist approach for statement 1 is 15=3X5, so my reasoning is n(n+2)=3X5. Only n=3 match to that equation, so I pick up D. Could you tell me any thing wrong from my reasoning? THX!
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Re: What is the value of the integer n....Exponents [#permalink] New post 03 Jan 2013, 02:13
Expert's post
curtis0063 wrote:
Bunuel wrote:
ajit257 wrote:
What is the value of the integer n?

(1) n(n + 2) = 15
(2) (n + 2)^n = 125



What is the value of the integer n?

(1) n(n + 2) = 15 --> n^2+2n-15=0 --> (n+5)(n-3)=0 --> n=-5 or n=3. Not sufficient.

Answer: B.


Dear Bunuel,

My fist approach for statement 1 is 15=3X5, so my reasoning is n(n+2)=3X5. Only n=3 match to that equation, so I pick up D. Could you tell me any thing wrong from my reasoning? THX!


You need to brush up fundamentals.

Chekc here: http://www.purplemath.com/modules/solvquad.htm and here: http://www.purplemath.com/modules/factquad.htm
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COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink] New post 02 Aug 2014, 12:06
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Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink] New post 04 Sep 2014, 06:10
curtis0063 wrote:
Bunuel wrote:
ajit257 wrote:
What is the value of the integer n?

(1) n(n + 2) = 15
(2) (n + 2)^n = 125



What is the value of the integer n?

(1) n(n + 2) = 15 --> n^2+2n-15=0 --> (n+5)(n-3)=0 --> n=-5 or n=3. Not sufficient.

Answer: B.


Dear Bunuel,

My fist approach for statement 1 is 15=3X5, so my reasoning is n(n+2)=3X5. Only n=3 match to that equation, so I pick up D. Could you tell me any thing wrong from my reasoning? THX!


15 can also be written as -3 * -5... if n= -5 then n(n+2) => -5 * -3= 15
So A cannot provide an unique solution.
Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n   [#permalink] 04 Sep 2014, 06:10
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