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Founder  Joined: 18 Apr 2015
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A perfect square is a positive integer which when square roo [#permalink]
Expert's post 00:00

Question Stats: 66% (00:56) correct 33% (00:00) wrong based on 12 sessions
A perfect square is a positive integer which when square rooted results in an integer. If $$N = 3^4 * 5^3 * 7$$, then what is the biggest perfect square that is a factor of $$N$$?

(A) $$3^2$$

(B) $$5^2$$

(C) $$9^2$$

(D) $$(9 * 5)^2$$

(E) $$(3 * 5 * 7)^2$$
[Reveal] Spoiler: OA

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GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests. Director  Joined: 07 Jan 2018
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Re: A perfect square is a positive integer which when square roo [#permalink]
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First notice that all the options are a perfect square. However we need the biggest among them. It can be seen easily that A<B<C<D therefore we can eliminate A, B and C. Now among D and E, D is bigger so it is the answer. Since both are square of some numbers in the bracket we can only compare the expression inside the bracket
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This is my response to the question and may be incorrect. Feel free to rectify any mistakes
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Senior Manager  Joined: 22 Jun 2019
Posts: 378
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Kudos [?]: 51 , given: 133

Re: A perfect square is a positive integer which when square roo [#permalink]
Carcass wrote:
A perfect square is a positive integer which when square rooted results in an integer. If $$N = 3^4 * 5^3 * 7$$, then what is the biggest perfect square that is a factor of $$N$$?

(A) $$3^2$$

(B) $$5^2$$

(C) $$9^2$$

(D) $$(9 * 5)^2$$

(E) $$(3 * 5 * 7)^2$$

need explanation

Last edited by huda on 07 Aug 2019, 01:47, edited 6 times in total.
Founder  Joined: 18 Apr 2015
Posts: 8933
Followers: 178

Kudos [?]: 2106 , given: 8289

Re: A perfect square is a positive integer which when square roo [#permalink]
Expert's post
Precisely, what did you not get sir in the explanation above ??

Regards
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Need Practice? 20 Free GRE Quant Tests available for free with 20 Kudos
GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests. Senior Manager  Joined: 22 Jun 2019
Posts: 378
Followers: 0

Kudos [?]: 51  , given: 133

Re: A perfect square is a positive integer which when square roo [#permalink]
1
KUDOS
Carcass wrote:
Precisely, what did you not get sir in the explanation above ??

Regards

later I got it but forgot to mention. Thanks for the concern. Intern Joined: 07 Feb 2019
Posts: 36
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Kudos [?]: 14  , given: 1

Re: A perfect square is a positive integer which when square roo [#permalink]
1
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Convert the options to prime factors

(A) $$3^2$$

(B) $$5^2$$

(C) $$3^4$$

(D) $$3^4 * 5^2$$

(E) $$(3 * 5 * 7)^2$$

D is clearly the biggest factor of N
Manager Joined: 18 Jun 2019
Posts: 124
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Kudos [?]: 22 , given: 62

Re: A perfect square is a positive integer which when square roo [#permalink]
I keep wondering isnt 3*5*7 sq bigger?
Founder  Joined: 18 Apr 2015
Posts: 8933
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Kudos [?]: 2106 , given: 8289

Re: A perfect square is a positive integer which when square roo [#permalink]
Expert's post
No

Regards
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GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests. Re: A perfect square is a positive integer which when square roo   [#permalink] 19 Aug 2019, 10:56
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