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Re: What is the value of the integer n....Exponents [#permalink]
30 Dec 2010, 16:45

5

This post received KUDOS

Expert's post

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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.

Re: What is the value of the integer n....Exponents [#permalink]
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.

Re: What is the value of the integer n....Exponents [#permalink]
01 Jan 2011, 07:18

Expert's post

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. _________________

Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink]
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. _________________

I am the master of my fate. I am the captain of my soul. Please consider giving +1 Kudos if deserved!

DS - If negative answer only, still sufficient. No need to find exact solution. PS - Always look at the answers first CR - Read the question stem first, hunt for conclusion SC - Meaning first, Grammar second RC - Mentally connect paragraphs as you proceed. Short = 2min, Long = 3-4 min

Re: What is the value of the integer n....Exponents [#permalink]
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!

Re: What is the value of the integer n....Exponents [#permalink]
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!

Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink]
02 Aug 2014, 12:06

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: What is the value of the integer n? (1) n(n + 2) = 15 (2) (n [#permalink]
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.

gmatclubot

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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