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If x & y are positive integers, is x*y a multiple of 8?

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nk2120
 Post subject: If x & y are positive integers, is x*y a multiple of 8?
 Post Posted: Sun Jan 04, 2009 3:24 pm 
(1) the Greatest Common Divisor of x and y is 10
(2) the Least Common Multiple of x and y is 100

Answer: C, both answers taken together can answer the question

can anybody explain? thanks!
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kylo
 Post subject:
 Post Posted: Thu Jan 08, 2009 8:35 am 
product of two numbers (a x b) = GCD (a&b) x LCM (a&b).


Thanks!
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RonPurewal
 Post subject:
 Post Posted: Fri Jan 09, 2009 9:17 am 
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ManhattanGMAT Staff


Posts: 7146
kylo wrote:
product of two numbers (a x b) = GCD (a&b) x LCM (a&b).


Thanks!


this is a cool fact that has also been posted elsewhere on this board.
it's somewhat obscure, but it's definitely useful; if you get the chance to apply it, it will almost certainly render the problem much, much easier.

by the way, i've never really understood the posting of "thanks" on posts such as this one. kylo, care to enlighten?
just curious.
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RonPurewal
 Post subject:
 Post Posted: Fri Jan 09, 2009 9:19 am 
Offline
ManhattanGMAT Staff


Posts: 7146
nk2120 wrote:
(1) the Greatest Common Divisor of x and y is 10
(2) the Least Common Multiple of x and y is 100

Answer: C, both answers taken together can answer the question

can anybody explain? thanks!


no.

you posted statements 1 and 2, but not the question. there is currently nothing to "explain".
what's the prompt question?
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kylo123
 Post subject: Re: If x & y are positive integers, is x*y a multiple of 8?
 Post Posted: Thu Mar 26, 2009 5:16 am 
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Students


Posts: 2
@RonPurewal -
i give "thanks" to all the people who post & discuss gmat related stuffs. It also gives me an oppurtunity to improve.
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StaceyKoprince
 Post subject: Re: If x & y are positive integers, is x*y a multiple of 8?
 Post Posted: Fri Apr 03, 2009 5:05 pm 
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ManhattanGMAT Staff


Posts: 6077
Location: San Francisco
Thanks, kylo - that's very nice of you!

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Stacey Koprince
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