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gcf and lcm problem
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04 Jun 2009, 21:41
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hey guys was wondering if someone could offer a way to solve this problem: If X and Y are integers, what is the value of xy? (1) The greates common factor of X and Y is 10 (2) The least common multiple of X and Y is 180 ANSWER: C. == Message from the GMAT Club Team == THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION. This discussion does not meet community quality standards. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.



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Re: gcf and lcm problem
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05 Jun 2009, 00:56
scorpio7 wrote: hey guys was wondering if someone could offer a way to solve this problem:
If X and Y are integers, what is the value of xy?
(1) The greates common factor of X and Y is 10
(2) The least common multiple of X and Y is 180
ANSWER: C. E 1) x and y could be a variety of numbers that include the primes 2 and 5 insuff 2) x and y could be a variety of numbers with prime factors that include 3,3,5,2,2 between the two together x and y must both contain 2 and 5, but there is only one 5 in 180 insufficient



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Re: gcf and lcm problem
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05 Jun 2009, 02:41
1) x and y could be 20 ,30/30,40......any number with 2,5 as factors insufficient 2) x and y could be a variety of numbers with prime factors that include 3,3,5,2,2 iNSUFFIENT TOGETHER x and y must have 2,5 as factors ; however the remaining factors can be adjusted in many ways iNSUFFIENT IMO E
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Re: gcf and lcm problem
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05 Jun 2009, 03:41
bigtreezl wrote: E
1) x and y could be a variety of numbers that include the primes 2 and 5 insuff 2) x and y could be a variety of numbers with prime factors that include 3,3,5,2,2 between the two
together x and y must both contain 2 and 5, but there is only one 5 in 180 insufficient I think we can find the value of XY Statement (1) says 2 and 5 are common factors of X and YInsufficient Statement (2) the LCM of X and Y is 180 which means 2,2,3,3, and 5 factors of X and YInsufficient Combining both the statements 2 5 2 3 3 2 5  GCF 2 x 5 = 10 (Greatest power of common multiples) LCM 2 x 5 x 2 x 3 x 3 = 180 (Least power of all the multiples) The only common primes between X and Y are 5, and 2. The remaining primes of LCM (2, 3, 3) will be primes of either X or Y and not both, because if it will be in both it will be multiplied to get the GCF. The number in this case would be 180*10 = 1800. Hence C is the answer Some good info on LCM and GCF http://www.purplemath.com/modules/lcm_gcf.htm



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Re: gcf and lcm problem
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05 Jun 2009, 06:07
humans wrote: bigtreezl wrote: E
1) x and y could be a variety of numbers that include the primes 2 and 5 insuff 2) x and y could be a variety of numbers with prime factors that include 3,3,5,2,2 between the two
together x and y must both contain 2 and 5, but there is only one 5 in 180 insufficient I think we can find the value of XY Statement (1) says 2 and 5 are common factors of X and YInsufficient Statement (2) the LCM of X and Y is 180 which means 2,2,3,3, and 5 factors of X and YInsufficient Combining both the statements 2 5 2 3 3 2 5  GCF 2 x 5 = 10 (Greatest power of common multiples) LCM 2 x 5 x 2 x 3 x 3 = 180 (Least power of all the multiples) The only common primes between X and Y are 5, and 2. The remaining primes of LCM (2, 3, 3) will be primes of either X or Y and not both, because if it will be in both it will be multiplied to get the GCF. The number in this case would be 180*10 = 1800. Hence C is the answer Some good info on LCM and GCF http://www.purplemath.com/modules/lcm_gcf.htmI agree. One of the properties of GCF and LCM is (GCF of A and B) * (LCM of A and B) = A*B. GCF consist of shared prime factors and LCM consist of nonshared prime factors. Together they both form the combined integer as demonstrated by humans. Answer is definitely C.



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Re: gcf and lcm problem
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05 Jun 2009, 09:58
the answer should be C. the product of 2 number= product of their Lcm and HCF



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Re: gcf and lcm problem
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05 Jun 2009, 23:39
humans wrote: bigtreezl wrote: E
1) x and y could be a variety of numbers that include the primes 2 and 5 insuff 2) x and y could be a variety of numbers with prime factors that include 3,3,5,2,2 between the two
together x and y must both contain 2 and 5, but there is only one 5 in 180 insufficient I think we can find the value of XY Statement (1) says 2 and 5 are common factors of X and YInsufficient Statement (2) the LCM of X and Y is 180 which means 2,2,3,3, and 5 factors of X and YInsufficient Combining both the statements 2 5 2 3 3 2 5  GCF 2 x 5 = 10 (Greatest power of common multiples) LCM 2 x 5 x 2 x 3 x 3 = 180 (Least power of all the multiples) The only common primes between X and Y are 5, and 2. The remaining primes of LCM (2, 3, 3) will be primes of either X or Y and not both, because if it will be in both it will be multiplied to get the GCF. The number in this case would be 180*10 = 1800. Hence C is the answer Some good info on LCM and GCF http://www.purplemath.com/modules/lcm_gcf.htmyeah..you're right..makes perfect sense == Message from the GMAT Club Team == THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION. This discussion does not meet community quality standards. It has been retired. If you would like to discuss this question please repost it in the respective forum. Thank you! To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative  Verbal Please note  we may remove posts that do not follow our posting guidelines. Thank you.



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Re: gcf and lcm problem
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