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# Hiii, This is my first post on gmatclub, I have learnt a lot

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Manager
Joined: 14 Mar 2011
Posts: 203
Followers: 6

Kudos [?]: 87 [0], given: 21

Hiii, This is my first post on gmatclub, I have learnt a lot [#permalink]  04 Jun 2011, 04:31
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Question Stats:

33% (02:14) correct 67% (00:46) wrong based on 9 sessions
Hiii, This is my first post on gmatclub, I have learnt a lot by reading the existing posts here. Please help me with this question.

If m and n are negative integers, what is the value of mn?

(1) m^n = 1/81

(2)n^m = - 1/64
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CEO
Joined: 17 Nov 2007
Posts: 3574
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 414

Kudos [?]: 2244 [0], given: 359

Re: If m and n are negative integers, what is the value of mn? [#permalink]  04 Jun 2011, 05:03
Expert's post
Welcome to the forum!

Edited

1) m^n = 1/81
81 = 9*9 = 3*3*3*3 --> m = -9, n = -2 (mn=18) or m=-3, n =-4 (mn=12). Insufficient.

2) n^m = -1/64
64 = 2*2*2*2*2*2 = 4*4*4 = 8*8 --> m has to be an odd integer to get negative result. m = -1, n = -64 (mn=64) or m=-3, n =-4 (mn=12) . Inufficient.

1&2) only mn=12. Sufficient

C
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Manager
Joined: 14 Mar 2011
Posts: 203
Followers: 6

Kudos [?]: 87 [2] , given: 21

Re: If m and n are negative integers, what is the value of mn? [#permalink]  04 Jun 2011, 05:23
2
KUDOS
Hii walker, thanks for the welcome and for the explanation. I did solved the A option correctly and concluded that it gave two options for mn. However I need a little more help, option B says -1/64, if question says 2 negative integers, wouldn't -64 ^ -1 also end being -1/64, then B too will have indefinite answer for mn. ( -3,-4) and (-1, -64) ?
CEO
Joined: 17 Nov 2007
Posts: 3574
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 414

Kudos [?]: 2244 [0], given: 359

Re: If m and n are negative integers, what is the value of mn? [#permalink]  04 Jun 2011, 05:34
Expert's post
You are right, I forgot about -1...
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Manager
Joined: 14 Mar 2011
Posts: 203
Followers: 6

Kudos [?]: 87 [0], given: 21

Re: If m and n are negative integers, what is the value of mn? [#permalink]  04 Jun 2011, 05:42
thanks for confirming that -64^ -1 is also a valid solution. In that case C should be the answer , as (-3,-4) appears in both options. However the original explanation too seemed to have missed (-64, -1) in B, the OE says only (-3,-4) as a solution for B. So OA was B. However I think C should be the answer. the question is from DS challenge set by jeff sackmann. This is only solution among all in his sets with which I am not feeling comfortable.
Re: If m and n are negative integers, what is the value of mn?   [#permalink] 04 Jun 2011, 05:42
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