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Integers

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Integers

by moneyman » Sun Oct 21, 2007 2:41 am
If x and y are positive integers , what is the value of xy??

(1)The greatest common factor of x and y is 10
(2)The least common multiple of x and y is 180
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by samirpandeyit62 » Sun Oct 21, 2007 4:16 am
If x and y are positive integers , what is the value of xy??

(1)The greatest common factor of x and y is 10

can be 20,30 30,50 etc INSUFF

(2)The least common multiple of x and y is 180

180 = 9 * 2 * 5 * 2

it can be 90,20 180,10 etc insuff

combine: here also we cannot say coz both these pairs have 10 as GCD

E
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Samir
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by agni_mba » Sun Oct 21, 2007 2:06 pm
I think the answer should be C.

10 GCD => X/10, Y/10 will be that part of X, Y which are uncommon between the two. This means if we multiply these two with 10, that would give me LCM.

i.e. X*Y/10 = 180 or X.Y=1800.

cheers
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by gmatguy16 » Sun Oct 21, 2007 3:40 pm
samir why do you think this rule does not apply here ,
gcd*lcm of two integers = product of two integers
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by ri2007 » Sun Oct 21, 2007 7:16 pm
samirpandeyit62 wrote:If x and y are positive integers , what is the value of xy??

(1)The greatest common factor of x and y is 10

can be 20,30 30,50 etc INSUFF

(2)The least common multiple of x and y is 180

180 = 9 * 2 * 5 * 2

it can be 90,20 180,10 etc insuff

combine: here also we cannot say coz both these pairs have 10 as GCD

E
Samir

Should the ans not be C?
Since we know GCF is 10 and LCM is 180 the only numbers possible are 10*2 and 10*9 or 10*18 and 10*1

product of both these pairs is the same 1800

To be honest once u write an ans i have developed a tendency not to question it...since its usually right:)) but would appreciate if u could take a look at it again

thanks
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by samirpandeyit62 » Sun Oct 21, 2007 8:56 pm
My bad, I somehow thought that we need values of x & y (did not have good concentration) but we require xy here so 90,20 & 180,10 will give the same results, so C should be the ans, Thanks agni_mba, gmatguy16 & RI for pointing out.

RI : As human beings no body is infallible & so am I, so please go ahead & correct me if I'm wrong, I would really appreciate that, thanks.
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Samir
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