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Manager  Joined: 01 Feb 2012
Posts: 85
If a, m and n are positive integers, is n^(2a) a multiple of  [#permalink]

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10 00:00

Difficulty:   75% (hard)

Question Stats: 51% (01:49) correct 49% (02:05) wrong based on 245 sessions

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If a, m and n are positive integers, is n^(2a) a multiple of m^a?

(1) n is a multiple of m/2
(2) n is a multiple of 2m

Originally posted by fireinbelly on 30 Apr 2013, 05:33.
Last edited by Bunuel on 30 Apr 2013, 05:40, edited 1 time in total.
Edited the question.
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Joined: 02 Sep 2009
Posts: 58391
Re: If a, m and n are positive integers, is n^(2a) a multiple of  [#permalink]

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If a, m and n are positive integers, is n^(2a) a multiple of m^a?

The question asks whether $$\frac{n^{2a}}{m^a}=(\frac{n^2}{m})^a=integer$$. So, the question basically asks whether n^2 is a multiple of m.

(1) n is a multiple of m/2. If n=3 and m=2, then n^2=9 is NOT a multiple of m=2 but if n=2 and m=2, then n^2=4 IS a multiple of m=2. Not sufficient.

(2) n is a multiple of 2m. This implies that n is a multiple of m, thus n^2 is also a multiple of m. Sufficient.

Hope it's clear.
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Manager  Joined: 26 Feb 2013
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Concentration: Strategy, General Management
GMAT 1: 660 Q50 V30 WE: Consulting (Telecommunications)
Re: If a, m and n are positive integers, is n^(2a) a multiple of  [#permalink]

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1
Option B.

From Stmt 1:
n is a multiple of m/2 . case 1:n= 9 , m=6 and a =1
9 is a multiple of 3(m/2) bur 81 is not a multiple of 6.

case 2 : n=8 , m=4 and a=1.
8 is a multiple of 2(m/2) and 8^2 = 64 is a multiple of 4.
so insufficient.

stmt 2:

n=2m*k. now both sides raised to the power or 2a gives
n^2a = 2^2a * k^2a * m^2a => 2^2a* k^2a * m^a* m^a

Hence it is a multiple of m^a. Sufficient
Intern  Joined: 23 Apr 2014
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Re: If a, m and n are positive integers, is n^(2a) a multiple of  [#permalink]

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1
The question basically asks if n^2a/m^a =integer,is (n^a.n^a)/m^a =integer,is (n/m)^a.n^a=integer,since n and a are positive integer,it will always be an integer,so the question really is n a multiple of m then only (n/m)^a.n^a=integer

Statement 1
n/(m/2)=integer↪2n/m=integer↪n=1,m=2 then n/m≠integer↪↪but n=2,m=1,then n/m=integer…not sufficient

Statement 2

n/2m=integer↪n/m=2*integer….sufficient

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Re: If a, m and n are positive integers, is n^(2a) a multiple of  [#permalink]

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_________________ Re: If a, m and n are positive integers, is n^(2a) a multiple of   [#permalink] 19 Oct 2018, 06:42
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