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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote If a and b are two positive numbers, what is the product of This topic has 2 expert replies and 2 member replies Top Member If a and b are two positive numbers, what is the product of Timer 00:00 Your Answer A B C D E Global Stats Difficult If a and b are two positive numbers, what is the product of a and b? 1) The LCM of a and b is 16 2) The GCD of a and b is 4 OA C Source: e-GMAT Top Member Legendary Member Joined 02 Mar 2018 Posted: 1121 messages Followed by: 2 members Product of numbers =product of L.C.M * product of GCD/H.C.F $$Statement\ 1=LCM\ of\ a\ and\ b\ =16$$ $$Given\ that\ L.C.M\ of\ a\ and\ b=16$$ 1 and 16; product will be 16 2 and 16; product will be 32 4 and 16; product will be 64 This product doesn't give a unique answer hence it is INSUFFICIENT $$statement2\ =\ GCD\ a\ and\ \ b\ =4$$ a and b could be = 4 and 8 ; product will be 32 4 and 12 ; product will be 48 4 and 16 ; product will be 64 There are more that 1 possible combination and statement doesn't give a unique answer hence statement 2 is INSUFFICIENT. statement 1 and 2 together product of numbers =LCM *GCD =16*4 =64 Both statements together are SUFFICIENT $$answer=option\ C$$ GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12995 messages Followed by: 1250 members Upvotes: 5254 GMAT Score: 770 BTGmoderatorDC wrote: If a and b are two positive numbers, what is the product of a and b? 1) The LCM of a and b is 16 2) The GCD of a and b is 4 Target question: What is the value of ab? Statement 1: The LCM of a and b is 16 Let's TEST some values. There are several values of a and b that satisfy statement 1. Here are two: Case a: a = 1 and b = 16 (the LCM of 1 and 16 is 16). In this case, the answer to the target question is ab = (1)(16) = 16 Case b: a = 2 and b = 16 (the LCM of 2 and 16 is 16). In this case, the answer to the target question is ab = (2)(16) = 32 Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT Statement 2: The GCD of a and b is 4 Let's TEST some more values. Case a: a = 4 and b = 4 (the GCD of 4 and 4 is 16). In this case, the answer to the target question is ab = (4)(4) = 16 Case b: a = 4 and b = 12 (the GCD of 4 and 12 is 16). In this case, the answer to the target question is ab = (4)(12) = 48 Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT Statements 1 and 2 combined --------ASIDE---------------------- There's a nice rule that says: (greatest common divisor of x and y)(least common multiple of x and y) = xy Example: x = 10 and y = 15 Greatest common divisor of 10 and 15 = 5 Least common multiple of 10 and 15 = 30 Notice that these values satisfy the above rule, since (5)(30) = (10)(15) --------BACK TO THE QUESTION! ---------------------- Statement 1 tells us that the LCM of a and b is 16 Statement 2 tells us that the GCD of a and b is 4 So, the product ab = (16)(4) = 64 So, the answer to the target question is ab = 64 Since we can answer the target question with certainty, the combined statements are SUFFICIENT Answer: C Cheers, Brent _________________ Brent Hanneson – Creator of GMATPrepNow.com Use my video course along with Sign up for free Question of the Day emails And check out all of these free resources GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months! GMAT/MBA Expert GMAT Instructor Joined 22 Aug 2016 Posted: 1984 messages Followed by: 30 members Upvotes: 470 BTGmoderatorDC wrote: If a and b are two positive numbers, what is the product of a and b? 1) The LCM of a and b is 16 2) The GCD of a and b is 4 OA C Source: e-GMAT Note that the product of two numbers equals the product of their LCM and GCD. Thus, we need both the statements. The correct answer: C Hope this helps! -Jay _________________ Manhattan Review GMAT Prep Locations: Hyderabad | Kukatpally | Bangalore | Anna Nagar | and many more... Schedule your free consultation with an experienced GMAT Prep Advisor! Click here. Newbie | Next Rank: 10 Posts Joined 17 Aug 2018 Posted: 9 messages Hi, This question tests the basic rule of L.C.M and H.C.F Rule: If “x” and “y” are two numbers, then Product of two numbers = Product of their L.C.M and H.C.F i.e., (x*y) = (L.C.M(x,y) * H.C.F(x,y)). Given in this question, Two numbers are “a” and “b”. Statement I insufficient: The LCM of a and b is 16 If a = 4 and b = 16, then LCM is 16 but the product of ab is 64 If a = 2 and b = 16, then LCM is 16 but the product of ab is 32. So not sufficient. Statement II insufficient: The GCD of a and b is 4 If a = 4 and b = 16, then GCD is 4 but the product of ab is 64 If a = 4 and b = 8, then GCD is 4 but the product of ab is 32. So not sufficient. Together it is sufficient. According to the rule, Product of two numbers = Product of their L.C.M and H.C.F So, Product of two numbers = 16*4 = 64 So the answer is C. • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

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