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Is 5^k less than 1,000? (1) 5^(k-1) > 3000 (2) 5^(k-1) =

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Director
Joined: 03 Jul 2003
Posts: 652
Is 5^k less than 1,000? (1) 5^(k-1) > 3000 (2) 5^(k-1) = [#permalink]

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12 Dec 2003, 16:07
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Is 5^k less than 1,000?
(1) 5^(k-1) > 3000
(2) 5^(k-1) = 5^k - 500
Manager
Joined: 12 Oct 2003
Posts: 247
Location: USA

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12 Dec 2003, 16:23
D

(1) 5^(k-1) > 3000
(5^k)/(5) > 3000
5^k > 15000

(2) 5^(k-1) = 5^k - 500
5^k/5 - 5^k = -500
5^k (1/5 - 1) = -500
5^k (-4/5) = -500
5^k = -500 * -5/4
5^k = 625
Director
Joined: 13 Nov 2003
Posts: 960
Location: Florida

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12 Dec 2003, 20:27
CEO
Joined: 15 Aug 2003
Posts: 3454

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13 Dec 2003, 00:07
Is 5^k less than 1,000?
(1) 5^(k-1) > 3000
(2) 5^(k-1) = 5^k - 500

(1) we get 5^k > 15000 ..clearly sufficient ....

(2) we get 5^k * 4/5 = 500 so.. 5^k = 2500/4 ..sufficient

D

weird question. we should get the same "Answer" with both?
GMAT Instructor
Joined: 07 Jul 2003
Posts: 770
Location: New York NY 10024
Schools: Haas, MFE; Anderson, MBA; USC, MSEE

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17 Dec 2003, 02:04
praetorian123 wrote:
Is 5^k less than 1,000?
(1) 5^(k-1) > 3000
(2) 5^(k-1) = 5^k - 500

(1) we get 5^k > 15000 ..clearly sufficient ....

(2) we get 5^k * 4/5 = 500 so.. 5^k = 2500/4 ..sufficient

D

weird question. we should get the same "Answer" with both?

That's not so weird of a question. This is not "advertised" but if you examine DS questions in the OG, you will NEVER find two answers that contradict each other. This is good to know for the GMAT because if you do find two answers that contradict each other, you did something wrong somewhere....
_________________

Best,

AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993

Re: G+ DS-17-20   [#permalink] 17 Dec 2003, 02:04
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