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

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airan: Master | Next Rank: 500 Posts; Posts: 127; Joined: Tue May 13, 2008 12:28 am; Thanked: 2 times; GMAT Score:710

by airan » Sat Jul 05, 2008 10:54 pm

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.

Thanks
Airan

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Source: Beat The GMAT — Data Sufficiency | Sat Jul 05, 2008 10:54 pm

wilderness: Master | Next Rank: 500 Posts; Posts: 102; Joined: Sat Mar 15, 2008 4:03 am; Thanked: 4 times

by wilderness » Mon Jul 07, 2008 12:22 pm

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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sethids: Master | Next Rank: 500 Posts; Posts: 135; Joined: Mon Jun 23, 2008 3:56 am; Thanked: 7 times

by sethids » Mon Jul 07, 2008 1:43 pm

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: Master | Next Rank: 500 Posts; Posts: 102; Joined: Sat Mar 15, 2008 4:03 am; Thanked: 4 times

by wilderness » Sat Jul 12, 2008 2:57 pm

thanks for the correction

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tzink: Senior | Next Rank: 100 Posts; Posts: 31; Joined: Thu Jul 10, 2008 9:02 pm; Thanked: 1 times

by tzink » Sat Jul 12, 2008 8:44 pm

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

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lion147: Senior | Next Rank: 100 Posts; Posts: 66; Joined: Sun Jul 06, 2008 9:14 am; Location: Florida; Thanked: 7 times; GMAT Score:710

by lion147 » Sat Jul 12, 2008 10:21 pm

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

No.

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