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GMAT PREP2 DS2

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Manager
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GMAT PREP2 DS2 [#permalink]

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08 Oct 2007, 12:07
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plz explain...thx
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Director
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08 Oct 2007, 12:25
I'm also getting B but since you've put this here I assume B is wrong.

Stat 1:
x = 40, y = 10, HCF = 10, xy is a multiple of 8.
x= 10, y = 10, HCF = 10, xy is not a multiple of 8.
Insuff.

Stat 2:
Since LCM of x and y is 100, the prime factorization of x & y has to be 2^2*5^2. This is never divisible by 8. Suff.

I'm not very sure of my analysis of the 2nd statement.
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Re: GMAT PREP2 DS2 [#permalink]

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08 Oct 2007, 12:46
12345678 wrote:
plz explain...thx

C it is.

The common factors in the two numbers are HCF.

The common factors in the two numbers + the remainders

LCD*GCD= product of the numbers.

St.1.....not sufficient numbers can be anything 10, 80, 40.....
some are multiple of 8 and some not though they still have the GCD of 10.

St.2 ....not sufficient. X and Y can be 100 and 1 ( not multiple of 8 though LCD is 100) or
X and Y can be 100 and 10 ( 1000 /8 =125, multiple of 8 and LCD is 100).

Both taken togather.....100( LCD)*10(GCD)=1000=XY
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Re: GMAT PREP2 DS2 [#permalink]

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08 Oct 2007, 12:53
rishi2377 wrote:
12345678 wrote:
plz explain...thx

C it is.

The common factors in the two numbers are HCF.

The common factors in the two numbers + the remainders

LCD*GCD= product of the numbers.

St.1.....not sufficient numbers can be anything 10, 80, 40.....
some are multiple of 8 and some not though they still have the GCD of 10.

St.2 ....not sufficient. X and Y can be 100 and 1 ( not multiple of 8 though LCD is 100) or
X and Y can be 100 and 10 ( 1000 /8 =125, multiple of 8 and LCD is 100).

Both taken togather.....100( LCD)*10(GCD)=1000=XY

well explained.. OA is C
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Re: GMAT PREP2 DS2 [#permalink]

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08 Oct 2007, 20:37
12345678 wrote:
plz explain...thx

Stmnt 1 :
GCD 10 , let the numbers be 10 20 , gcd = 10 , product 200 divisible by 8
let the numbers be 10 30 , gcd = 10 , product 300 not divisible by 8

So not suff

Stmnt 2 :
GCD 10 , let the numbers be 2 50 , lcm = 100 , product 100 not divisible by 8
let the numbers be 100 10 , lcm = 100 , product 1000 divisible by 8

So not suff

Combining ,
product = lcm * gcd = 1000 is divisible by 8

C
Re: GMAT PREP2 DS2   [#permalink] 08 Oct 2007, 20:37
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