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If the positive square root of the product of 3 numbers ...


 
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airan
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PostPosted: Sat Jul 05, 2008 11:54 pm    Post subject: If the positive square root of the product of 3 numbers ... Reply with quote

If the positive square root of the product of 3 numbers is the largest of the 3 different numbers, what is the product of the 2 smallest numbers

(1) The largest number is 12.
(2) The average( arithematic) if the 3 numbers is 20/3.

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wilderness
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PostPosted: Mon Jul 07, 2008 1:22 pm    Post subject: Reply with quote

IMHO the answer is D

Let x y z be the 3 integers and let X be the biggest one.
beacase sqrt (xyz) = x
xyz = x^2

So yz = x i.e. the product of the smaller numbers is equal to the bigger number.

I. If x=12 then yz=12. SUFFICIENT

2. Says x+y+z=20
The only combination of integers I could find was 2,6,12 and hence the product of 2 small numbers is 12. SUFFICIENT.

So both are sufficient alone.
Did anyone find another combination of numbers that satisfies (2).
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PostPosted: Mon Jul 07, 2008 2:43 pm    Post subject: Reply with quote

wilderness wrote:
IMHO the answer is D

Let x y z be the 3 integers and let X be the biggest one.
beacase sqrt (xyz) = x
xyz = x^2

So yz = x i.e. the product of the smaller numbers is equal to the bigger number.

I. If x=12 then yz=12. SUFFICIENT

2. Says x+y+z=20
The only combination of integers I could find was 2,6,12 and hence the product of 2 small numbers is 12. SUFFICIENT.

So both are sufficient alone.
Did anyone find another combination of numbers that satisfies (2).


The GMAT maths section instructions indicate that all numbers used are real numbers unless otherwise specified...
In this question, there is no mention in the stem that the numbers in question are integers, therefore the second statement is not sufficient in itself.

IMO A is the answer... Please comment.
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wilderness
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PostPosted: Sat Jul 12, 2008 3:57 pm    Post subject: Reply with quote

thanks for the correction
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PostPosted: Sat Jul 12, 2008 9:44 pm    Post subject: Reply with quote

soo.. just for the record, it's NOT safe to assume that all GMAT numbers are integers?
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PostPosted: Sat Jul 12, 2008 11:21 pm    Post subject: Reply with quote

tzink wrote:
soo.. just for the record, it's NOT safe to assume that all GMAT numbers are integers?


No.
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