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Is x and y are positive integers, what is the value of xy? [#permalink]
 26 Apr 2008, 08:24
Question Stats:
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90% (00:56) wrong based on 0 sessions
Is x and y are positive integers, what is the value of xy?
(i) The greatest common factor of x and y is 10
(ii) The least common multiple of x and y is 180
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Re: DS - greatest common factor and least common multiple [#permalink]
26 Apr 2008, 08:55
quiet888 wrote: Is x and y are positive integers, what is the value of xy?
(i) The greatest common factor of x and y is 10
(ii) The least common multiple of x and y is 180 these question ans choice is always either C or E.. lets see.. xy? 1) gcd is 10 x=10 y=20 GCD =10 xy=200 x=10 y=60 GCD=10, xy=600 2) LCM x=180 y=2 LCM=180 xy=360 x=180 y=180 LCM=180 xy=180^2 Insuf together suppose x=180 y=10 suppse x=90 y=20 xy= is the same..Sufficient C it is.
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Re: DS - greatest common factor and least common multiple [#permalink]
26 Apr 2008, 11:50
another thing..with these type of question where we have the GCD and LCM..usually we can tell something like an XY but we cant really tell what X is or what y is...
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Re: DS - greatest common factor and least common multiple [#permalink]
27 Apr 2008, 14:27
anyway to solve this in under 2mins? fresh?
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Re: DS - greatest common factor and least common multiple [#permalink]
27 Apr 2008, 19:17
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jimmyjamesdonkey wrote: anyway to solve this in under 2mins? fresh? Yes, even under 20 seconds if you remember that xy = GCD*LCM. Sure! 
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Re: DS - greatest common factor and least common multiple [#permalink]
28 Apr 2008, 07:25
Woah can you elaborate that a little bit...I always have such problems with GCF & LCM..
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Re: DS - greatest common factor and least common multiple [#permalink]
19 Jul 2011, 00:30
FN wrote: quiet888 wrote: Is x and y are positive integers, what is the value of xy?
(i) The greatest common factor of x and y is 10
(ii) The least common multiple of x and y is 180 these question ans choice is always either C or E.. lets see.. xy? 1) gcd is 10 x=10 y=20 GCD =10 xy=200 x=10 y=60 GCD=10, xy=600 2) LCM x=180 y=2 LCM=180 xy=360 x=180 y=180 LCM=180 xy=180^2 Insuf together suppose x=180 y=10 suppse x=90 y=20 xy= is the same..Sufficient C it is. hi, For (ii) The least common multiple of x and y is 180 isn't x*y = 5400? my rational... if 180 is the Lowest Common Multiple, meaning that both x and y have 3, 3, 5, 2, 2 at least appeared twice for x y. So if x = 2, ?, 3, 5 y = 2, ?, 3, 5 ------------- x & y's LCM which is 180 = 2* 3* 5* ?* ?* So after pulling 5 & 3 & 2, we still need one 2 and one 3 to fulfil the 3, 3, 5, 2, 2 = (180) requirement. Having said that, the ? in each x & y should be 2 and 3. So multiple all 8 digits, it should x*y = 2* 2* 3* 5* 2* 3*3* 5* = 5400?
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Re: DS - greatest common factor and least common multiple [#permalink]
01 Aug 2011, 08:31
Could some body help me to understand this a little better.
here is where I am getting stuck
GCF = 10, There for X = 10A nd Y = 10B where A and B are separate constants
for example 20 and 30, here the GDF is 10 and a = 2 and b = 3
sice we dont have a and b from this equation. this is insufficient
statement 2:
LCM is 180
so X*N1 = 180 and Y * N2 = 180
since we do not know the values of N1 and N2 this statement is not sufficient.
even if we combine, we dont have information to solve.
I see come body explaining the answer are LCM*GCD. Could you please tell me how you arrived at that equation
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Re: DS - greatest common factor and least common multiple [#permalink]
01 Aug 2011, 09:38
GCF * LCM = X*Y it's a general rule
10*180 = 1800
so the the answer is C and u need less than 10 seconds
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Re: DS - greatest common factor and least common multiple [#permalink]
01 Aug 2011, 10:04
Always; if we multiply two positive integers then the multiplication is same as the multiplication of their lcm and gcf. In this case lcm = 180 and gcf = 10 hence xy = (lcm)(gcf) = 180.10 = 1800
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Re: DS - greatest common factor and least common multiple [#permalink]
02 Aug 2011, 10:44
manishgeorge wrote: Could some body help me to understand this a little better.
here is where I am getting stuck
GCF = 10, There for X = 10A nd Y = 10B where A and B are separate constants
for example 20 and 30, here the GDF is 10 and a = 2 and b = 3
sice we dont have a and b from this equation. this is insufficient
statement 2:
LCM is 180
so X*N1 = 180 and Y * N2 = 180
since we do not know the values of N1 and N2 this statement is not sufficient.
even if we combine, we dont have information to solve.
I see come body explaining the answer are LCM*GCD. Could you please tell me how you arrived at that equation it's a general rule and can always applied . if u want the details about how we arrived at that equation just let me know
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How can i lose my faith in life's fairness when i know that the dreams of those who sleep on the feathers are not more beautiful than the dreams of those who sleep on the ground? - Jubran Khaleel Jubran
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Re: DS - greatest common factor and least common multiple
[#permalink]
02 Aug 2011, 10:44
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