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brief expl from me 1 - clearly not suff, and we got that cd=2b 2 - clearly not suff, and we got that |b^3|=27 cause what if c negative? so we can't say for sure that b=3 like stated in OA. Am I right?

Re: a, b, c, and d are integers; abcd≠0 [#permalink]
16 Jan 2012, 01:09

2

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a, b, c, and d are integers; abcd >< 0; what is the value of cd? 1) c/b = 2/d 2) b^3*a^4*c = 27*a^4*c

SOLUTION:

statement 1: c/b = 2/d cd = 2b, we don't know the value of b. so. we can't find the value of cd. NOT SUFFICIENT

statement 2 : b^3*a^4*c = 27*a^4*c ==> a^4 * c (b^3-27) = 0 it means, a^4 =0 or c =0 or b^3 =27 so, b = 3 so, here we can get different values of cd. NOT SUFFICIENT

after combining both statement , we can get value of cd = 2b =6

Hence the ans is C.

I HOPE IT WILL BE HELPFUL. PS: EDITED after bunuel explanation _________________

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Last edited by 321kumarsushant on 16 Jan 2012, 02:30, edited 2 times in total.

Re: a, b, c, and d are integers; abcd≠0 [#permalink]
16 Jan 2012, 02:33

@bunuel thanks for explanation. it looks that my mind was somewhere else while solving the question. many times i misses an obvious point , main reason never to the 51 in Quant. i will have to focus more.

anyway, i have edited my explanation. _________________

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Attitude determine everything. all the best and God bless you.

Re: a, b, c, and d are integers; abcd≠0 [#permalink]
13 Sep 2012, 07:12

1

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Bunuel wrote:

a, b, c, and d are integers; abcd≠0; what is the value of cd?

(1) c/b = 2/d --> cd=2b, we don't know the value of b to get the single numerical value of cd. Sufficient.

(2) b^3*a^4*c = 27*a^4*c --> as a and c does not equal to zero we can safely reduce both parts by a^4*c --> b^3=27 --> b=3. Not sufficient.

(1)+(2) As from (1) cd=2b and from (2) b=3 then cd=2b=6. Not sufficient.

Answer:C.

As for your question:

Runner2 wrote:

2 - clearly not suff, and we got that |b^3|=27 cause what if c negative? so we can't say for sure that b=3 like stated in OA. Am I right?

Odd roots have the same sign as the base of the root. For example, \sqrt[3]{125} =5 and \sqrt[3]{-64} =-4.

So \sqrt[3]{27}=3 and not -3 --> 3^3=27 and (-3)^3=-27.

Hope its' clear.

Hi Bunuel,

There is a slight typing error in the explanation. Statement "(1) c/b = 2/d --> cd=2b, we don't know the value of b to get the single numerical value of cd. Sufficient." should read "(1) c/b = 2/d --> cd=2b, we don't know the value of b to get the single numerical value of cd. Insufficient."

Correct me if i am wrong. _________________

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Re: a, b, c, and d are integers; abcd≠0 [#permalink]
13 Sep 2012, 07:18

Expert's post

fameatop wrote:

Bunuel wrote:

a, b, c, and d are integers; abcd≠0; what is the value of cd?

(1) c/b = 2/d --> cd=2b, we don't know the value of b to get the single numerical value of cd. Sufficient.

(2) b^3*a^4*c = 27*a^4*c --> as a and c does not equal to zero we can safely reduce both parts by a^4*c --> b^3=27 --> b=3. Not sufficient.

(1)+(2) As from (1) cd=2b and from (2) b=3 then cd=2b=6. Not sufficient.

Answer:C.

As for your question:

Runner2 wrote:

2 - clearly not suff, and we got that |b^3|=27 cause what if c negative? so we can't say for sure that b=3 like stated in OA. Am I right?

Odd roots have the same sign as the base of the root. For example, \sqrt[3]{125} =5 and \sqrt[3]{-64} =-4.

So \sqrt[3]{27}=3 and not -3 --> 3^3=27 and (-3)^3=-27.

Hope its' clear.

Hi Bunuel,

There is a slight typing error in the explanation. Statement "(1) c/b = 2/d --> cd=2b, we don't know the value of b to get the single numerical value of cd. Sufficient." should read "(1) c/b = 2/d --> cd=2b, we don't know the value of b to get the single numerical value of cd. Insufficient."