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value of mn [#permalink]

29 Dec 2011, 08:45

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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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Re: value of mn [#permalink]

29 Dec 2011, 10:18

C

What's your doubt?

1.
m=-3,n=-4; m=-9, n=-2
mn=12; mn=18
2.
n=-64,m=-1; n=-4, m=-3 [m will always be odd]
nm=64; mn=12

1+2
nm=12
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Re: value of mn [#permalink]

29 Dec 2011, 19:49

no doubt. just double checking as the OA was B.

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Re: value of mn [#permalink]

30 Dec 2011, 00:48

the answer is B

consider the first statement

u have m^n=1/81 cz both m and n are negative i.e. it should be (-ve)^(-ve) or in this case (-9)^(-2) or (-3) ^(-4) both of which satisfy the statement
thus Insufficient

consider the 2nd statement

we have n^m= -(1/64)

so the options can be (-8)^(-2) or (-4)^(-3)

cz minus sign is already there that means the exponent has to be odd (that is the only way we would get a negative sign out of the base.
thus we have only one solution (-4)^(-3) which give n=-4 and m=-3 or mn=12 hence
Sufficient

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Re: value of mn [#permalink]

30 Dec 2011, 01:34

puneetkr wrote:

the answer is B
consider the 2nd statement

we have n^m= -(1/64)

so the options can be (-8)^(-2) or (-4)^(-3)

there can one more solution: (-64)^(-1)
it should be C) imo

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Re: value of mn [#permalink]

30 Dec 2011, 07:09

d3thknell wrote:

puneetkr wrote:

the answer is B
consider the 2nd statement

we have n^m= -(1/64)

so the options can be (-8)^(-2) or (-4)^(-3)

there can one more solution: (-64)^(-1)
it should be C) imo

Yes It should be C...
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Re: value of mn [#permalink] 30 Dec 2011, 07:09

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value of mn

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